Modeling using VBA
Covered materials
-
Userforms
Controls
Module
Procedures & Functions
Variables
Scope
Variant “Data Type”
• In VB you don’t have to declare variable before its
usage
– Then, VB will by itself declare such variable as “Variant”
• You can also declare variable as “Variant”
– Dim myVar as Variant
• Variant – means that the variable may contain any data
type
Variables Assignment
• To assign a value to a Numeric or String type
Variable, you simply use your Variable name,
followed by the equals sign (=) and then the
String or Numeric
• To assign an Object to an Object type variable
you must use the key word "Set"
Variables Assignment – cont.
Sub ParseValue )(
Dim varName as String
varName = “Cuong Do”
Dim varAge as Integer
varAge = “28”
Dim varCell as Range
Set varCell = Range("A1")
varCell.Value = “123”
End Sub
VBA Variables Scope & Lifecycle
The scope & lifecycle of a variable defines the code where the
variable can be accessed and time when the stored data is kept
inside the variable
• Procedure-Level
– Variables defined inside procedures
– Can be accessed only inside the procedure and keep their data until the
End statement of the procedure
• Module-Level
– Defined in the top of a Module
– Any procedure inside the Module can access the variable
– The variable retains the values unless the Workbook closes
• Project-Level, Workbook Level, or Public Module-Level
– Defined as “Public” in the top of a Module
– Can be accesses by any procedure in any module
– The variable retains the values unless the Workbook closes
VBA Variables Scope & Lifecycle –
cont.
• Sub scopeExample()
Dim x as Integer
Procedure level variables
x=5
End Sub
Module level variables
• Dim y as Integer
‘all the module procedures are here…
Project level variables
• Public z as Integer
‘all the module procedures are here…
Which variable?
Module1
Userform8
How to address public variables?
Module1
Userform8
Basic Excel Classes
• Workbook: the class represents an Excel file
• Worksheet: represents a single worksheet
• Cell: represents a single cell
Excel Containers
• Workbooks: a collection of objects of class
“Workbook”
• Worksheets: a collection of objects of class
“Worksheet”
• Range: a range of objects of class Cell
Referring to Cells by Using a Range
Object
Sub Random()
Dim myRange As Range Set myRange =
Worksheets("Sheet1").Range("A1:D5")
myRange.Formula = "=RAND()"
myRange.Font.Bold = True
End Sub
Referring to Cells by Using a Range
Object
Sub Test1()
Range("A10").Value = "123"
End Sub
Sub Test2()
Set varRange = Range("A10")
varRange.Value = "123"
End Sub
Sub Test3()
Worksheets(1).Range("A10") = "123"
End Sub
Sub Test4()
Worksheets("Sheet1").Range("A10") = "123"
End Sub
Same
outcome
here
Referring to Multiple Ranges
Sub ClearRanges() Worksheets("Sheet1")._
Range("C5:D9,G9:H16,B14:D18").ClearContents
End Sub
Referring to Cells by Using Index
Numbers
• Cells indexing format:
– Cells(row, column), where both row and column are given
as integers (starting from 1)
Sub EnterValue()
Worksheets("Sheet1").Cells(6, 1).Value = 10
End Sub
– Cells(index)
Sub EnterValue()
Worksheets(1).Range("A1:D3").Cells(7) .Value = "Here it is"
End Sub
Referencing Cells Relative to Other
Cells
ActiveCell.Offset(1, 2).Value = "Here it is"
Some useful methods/properties
of Excel Classes
• Workbooks.Close – closes the active workbook
• Workbooks.Count – returns the number of currently
open workbooks
• Range(“A1”) is the same as Range(“A1”).Value
• Cells(1,1) is the same as Cells(1,1).Value
• Worksheets(1).Column(“A:B”).AutoFit
• Worksheets(1).Range(“A1:A10”).Sort_
• Workbooks.Open fileName:=“test.xls”
Arrays
Dim Students(1 to 5) As String
Students(1) = “Jack”
Students(2) = “Nick”
Multidimensional Arrays
Dim Grades(1 to 5,1 to 2)
Grades(1,1)=“Jack”
Grades(1,2)=“A”
Grades(2,1)=“Nick”
Grades(2,2)=“B”
For i=1 to 2
MsgBox Grades(i,1) & “ got ” & Grades(i,2)
Next
MsgBox Grades(1, 1) & " got " & Grades(1, 2) & vbCrLf & _
Grades(2, 1) & " got " & Grades(2, 2)
Resizing the Arrays
Dim Grades(1 to 5,1 to 2)
Grades(1,1)=“Jack”
Grades(1,2)=“A”
Grades(2,1)=“Nick”
Grades(2,2)=“B”
‘ Now ReDim the array
ReDim Grades(1 to 10,1 to 2) ‘previous values won’t be kept
ReDim Preserve Grades(1 to 10,1 to 2) ‘preserve previous values
Only the first dimension
can be changed!
Upper & Lower Index Bounds of an
Array
• Dim A(3): index from 0 to 3
• Dim A(1 to 3): index from 1 to 3
• Dim A(1 To 100, 0 To 3, -3 To 4)
– UBound(A, 1) – will return “100”
– UBound(A, 2) – will return “3”
– UBound(A, 3) – will return “4”
– LBound(A, 1) – will return “1”
– LBound(A, 2) – will return “0”
– LBound(A, 3) – will return “-3”
VBA Control Structures - If
• If Grade >= 90 Then
MsgBox "You got an A"
ElseIf Grade >= 80 Then
MsgBox "You got a B"
ElseIf Grade >= 70 Then
MsgBox "You got a C"
Else
MsgBox "You are out of scope”
Need to capture the rest of cases
End If
VBA Control Structures – Select
• Select Case Grade
Case Is >= 90
MsgBox "You got an A
Case Is >= 80
MsgBox "You got an B”
Case Is >= 70
MsgBox "You got a C”
Case Else
MsgBox "You out of scope”
Need to capture the rest of cases
End Select
VBA Control Structures – Loops
N!
Sub factorial2()
Dim N
N = 10
i=N
Cells(1, 2) = 1
Do While i >= 1
Cells(1, 2) = Cells(1, 2) * i
i=i-1
Loop
End Sub
Loop at least once
Sub factorial1()
Dim N
N = 10
Cells(1, 1) = 1
For i = N To 1 Step -1
Cells(1, 1) = Cells(1, 1) * i
Next
End Sub
Sub factorial3()
Dim N
N = 10
i=N
Cells(1, 3) = 1
Do
Cells(1, 3) = Cells(1, 3) * i
i=i-1
Loop While i >= 1
End Sub
Loops for Collection Objects
Sub WorkSheetsLoop()
Dim mySheet As Worksheet
For Each mySheet In Worksheets
MsgBox mySheet.Name
Next mySheet
End Sub
Nested Loops Example
Sub NestedLoopExample)(
For i = 1 To 5
For j = 1 To 5
Cells(i, j) = "Row " & i & " Col " & j
Next j
Next i
End Sub
Worksheet functions
Sub FuncExample()
Range("D6") = Application. WorksheetFunction. Sum(Range("D1:D5"))
‘ Can also use Application. Sum for short
End Sub
‘ Another way to get the sum
Range("D6").Formula = "=SUM(D1:D5)"
Other Issues in VBA programming
• What if need to pass an array of arguments
without knowing the number of arguments
Graphs
Graphs
Private Sub cmdGenerate_Click()
Range("B2:E13").Formula = "=RAND()*100"
End Sub
Private Sub cmdPlot_Click()
Create_Chart_Sheet
End Sub
Sub Create_Chart_Sheet()
Charts.Add
With ActiveChart
.ChartType = xlColumnClustered
.SetSourceData Source:=Sheets("Sheet4").Range("B1:E13")
End With
End Sub
Graphs (Columnclusted)
Graphs (BarStacked)