Excel VBA - City University Continuing Education
VBA for Microsoft Excel – Part 10
Contents
1
2
3
4
5
6
7
8
1
Protecting VBA projects ................................................................................ 1
Protecting Worksheets................................................................................... 2
2.1
Protecting the active sheet ....................................................................... 2
2.2
Protecting all the sheets using for each ................................................... 2
Error handling ................................................................................................ 2
3.1
The basic method to handle errors ........................................................... 2
3.2
Advanced example ................................ Error! Bookmark not defined.
Module level variables .................................................................................. 3
Constants ......................................................................................................... 4
Application object .......................................................................................... 4
Events .............................................................................................................. 4
7.1
The Worksheet_Change Event ................................................................ 4
Printing ............................................................................................................ 4
Protecting VBA projects
You can protect a VBA project to prevent unauthorised access to your code.
1.
2.
Open the Visual Basic Editor
Right-click the Project (corresponding to the filename) to be protected …
3.
4.
and choose VBAProject Properties
Choose the Protection tab
5.
Make sure that Lock Project for viewing is turned on and type in a
password (twice), then choose OK
The code associated with this project can still be seen after you have done
this. To verify the password protection, close the file, then re-open it.
1.
2.
In VBE double-click the icon for the password-protected project
To view it you must type the password into the box
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Excel VBA - City University Continuing Education
2
Protecting Worksheets
2.1 Protecting the active sheet
The Protect Sheet button is on the Review ribbon.
3
Error handling
ActiveSheet.Protect "abcd" True, True, True
3.1 The basic method to handle errors
An error situation that arises during the running of a macro is known as a runtime error. The following discussion deliberately contrives an error. The code
selects a cell five rows above the current cell and colours it yellow – if there
aren’t five rows above the current cell when the macro is run a run-time error
occurs.
You can probably guess that ActiveSheet is the object and Protect the
method; Protect takes various arguments, including Password, followed
by what aspects of the worksheet are being protected – the values are True
or False. In the example the password is ‘abcd’ (case sensitive)
Sub Macro1()
ActiveCell.Offset(-5, 0).Select
ActiveCell.Interior.Color = vbYellow
End Sub
The corrsesponding line to UnProtect it is
ActiveSheet.UnProtect "abcd" True, True, True
It is important to try to anticipate user errors. The most basic way is to add
some code that quits the macro.
2.2 Protecting all the sheets using for each
Now let us create a macro to protect all the sheets in the workbook. A For
Each loop can make the macro work for all sheets, with the following syntax.
Sub Macro1()
On Error GoTo myErrorHandler
A line of code to protect the current sheet might look
like this.
For Each variable In collection
Action(s) required
Next variable
Sub ProtectSheets()
Dim wk As Worksheet
For Each wk in Worksheets
wk.Protect “abcd”
Next wk
End Sub
ActiveCell.Offset(-5, 0).Select
ActiveCell.Interior.Color = vbYellow
this line means ‘if an error
occurs go to the line
specified by the provided
label’ – here
myErrorHandler is the
label
myErrorHandler:
Exit Sub
a label is some text and a
colon
End Sub
Of course this may leave the user none the wiser so you could add a message
box; it’s intuitive to think you do this just before the Exit Sub statement
myErrorHandler:
MsgBox "You must start below Row 5"
Exit Sub
End Sub
but this would cause the message box to appear each time the macro runs.
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Excel VBA - City University Continuing Education
There is nothing special about the label that stops the execution of the
statements after it – therefore even if the macro completes successfully, the
End Sub statement never happens, the macro terminates with the Exit Sub
statement. The answer lies with the keyword Resume.
4
Sub Macro1()
On Error GoTo myErrorHandler
To declare a module level variable, you declare it in the Declarations section
(where the Option statements are), before any subs.
ActiveCell.Offset(-5, 0).Select
ActiveCell.Interior.Color = vbYellow
exit_here:
Exit Sub
You can use Dim as previously, but it is recommended you use the keywords
Private or Public to determine the scope of the variable. Private variables are
accessible only to the subs in the same module, Public variables are accessible
to all the subs in the workbook. Here is a basic example that uses a global
variable:
myErrorHandler:
MsgBox "You must start below Row 5"
Option Explicit
Private x As Integer
Resume exit_here
Sub one()
x = 1
MsgBox x
End Sub
End Sub
If you want a message box to return the ‘official’ error number and
description, use the Err object as follows:
MsgBox Err.Number & " " & Err.Description
In case you are interested the above macro could be amended as follows:
If ActiveCell.Row > 5 Then ActiveCell.Offset(-5, 0).Select
Resume Next
You may want a macro to continue in spite of an error. The statement:
On Error Resume Next
means ‘clear the error and continue with the next line of the macro’. For
example you may want to continue calculating down a column even if one
calculation fails because of, say, a division by zero error. Another common
practice is to ensure that application defaults are restored by the error
handler.
Module level variables
Use module level variables only when two or more subs need access to the
same variable; otherwise it’s better practice to use variables local to the
procedure they are in.
Sub two()
x = x + 99
MsgBox x
End Sub
Sub runthisprog()
Call one
Call two
End Sub
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Excel VBA - City University Continuing Education
5
Constants
You can declare Constants as well as variables, the difference being that a
constant cannot change. The distinction between Public and Private applies as
for variables. Constants can be of a scientific nature, e.g.
Public Const Pi = 3.14159
or you can define your own preferred colours
Public Const myred = 5066944
or you can predefine file locations
Public Const myPath = “C:\Spreadsheets\”
6
Application object
Application has useful properties/methods that can improve various aspects
of a macro. The following are Boolean, i.e. set them to True or False.
Application.ScreenUpdating switches off the visual display when a macro is
running. Note that using Step Into is impossible if ScreenUpdating is set to
False.
Application.DisplayAlerts can be set to False while a macro is running to stop
Excel messages interfering with the smooth running of the macro. It is
essential to set it back to True before the End Sub, otherwise this setting will
persist.
Application.GeSaveAsFilename displays the File Save As window
Sub SaveName()
Dim fileSaveName As String
Workbooks.Add
fileSaveName = Application.GetSaveAsFilename _
(fileFilter:="Excel Files (*.xl*), *.xl*")
If fileSaveName <> False Then
MsgBox "Save as " & fileSaveName
End If
End Sub
7
Events
7.1 The Worksheet_Change Event
This event occurs when the value of a cell on the worksheet changes. You
could exploit it if you have volatile data. The code example simulates a
worksheet with external links like prices or exchange rates. A change to any
value triggers a colour change for every cell on the worksheet.
Private Sub Worksheet_Change(ByVal Target As Range)
Dim rng As Range
For Each rng In Range("prices")
If IsNumeric(rng) And Not IsEmpty(rng) Then
If rng >= 16 Then
rng.Font.Color = vbGreen
ElseIf rng < 15 Then
rng.Font.Color = vbRed
Else
rng.Font.Color = vbBlack
End If
End If
Next rng
End Sub
8
Page Setup and Printing
Every worksheet has its own PageSetup, therefore it follows that the
Worksheet object contains the PageSetup object
Page orientation, settings for margins etc. are properties of the PageSetup
object, e.g.,
Worksheets("Exams").Activate
With ActiveSheet.PageSetup
.Orientation = xlLandscape
.LeftMargin = Application.InchesToPoints(2.5)
.HeaderMargin = Application.InchesToPoints(0.3)
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Excel VBA - City University Continuing Education
.CenterHorizontally = True
.Zoom = 150
.LeftFooter = ThisWorkbook.FullName
.RightFooter = Application.UserName
End With
ActiveSheet.PrintPreview
' or ActiveSheet.PrintOut
Print Areas
By default the whole worksheet is printed. To designate a worksheet area to
be printed use the PrintArea property of PageSetup, e.g.,
ActiveSheet.PageSetup.PrintArea = "$A$1:$C$10"
For more flexibility you can use the Address property of Selection
ActiveSheet.PageSetup.PrintArea = Selection.Address
You can use the comma as the Union operator
ActiveSheet.PageSetup.PrintArea = "$A$1:$C$10,$C$2:$C$12"
BeforePrint event
You can use the BeforePrint event of the workbook make changes to
PageSetup every time any worksheet is printed.
Private Sub Workbook_BeforePrint(Cancel As Boolean)
Dim wk As Worksheet
Dim CompanyName As String
CompanyName = "City University"
For Each wk In Worksheets
With wk.PageSetup
.LeftFooter = CompanyName
.RightFooter = ThisWorkbook.FullName
End With
Next wk
End Sub
.
To clear a Print Area the code is
ActiveSheet.PageSetup.PrintArea = ""
Page Breaks
To add manual Page Breaks use HPageBreaks or VPageBreaks. For example to
add page breaks before the active cell:
ActiveSheet.HPageBreaks.Add Before:=ActiveCell
ActiveSheet.VPageBreaks.Add Before:=ActiveCell
To clear Page Breaks use
ActiveSheet.ResetAllPageBreaks
There are only objects for manual Page Breaks. To control automatic Page
Breaks the only way is to change the page margins
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