Hi, I have this code below that auto fills as Combo Box when the Spreadsheet Opens. It works great, but there is one issue I have with it. As if the Combo Box is changed once the Spreadsheet is open then it auto changes the cell on a particular worksheet. I have tried calling this function from the workbook open but just doesnt work. How can I get around this?

Private Sub Workbook_Open()
Application.ScreenUpdating = False
Dim intCount As Integer
'Populate Multi Column Combo Box - Installs Report
'***************************************
With Sheet1.cboInstallMonths
.Visible = False
.Clear
.ColumnCount = 2
.ColumnWidths = 0
.AddItem "1"
.List(.ListCount - 1, 1) = "January"
For intCount = 2 To 12 '
.AddItem (intCount)
.List(.ListCount - 1, 1) = MonthName(intCount)
Next
.Value = Val(DatePart("m", VBA.Date - 1))
.Visible = True
End With
With Sheet1
Select Case .cboInstallMonths.Value
Case 3, 6, 9, 12
booWeekType = True
Case Else
booWeekType = False
End Select
End With
End Sub

This is on the relevant Worksheet

Private Sub cboInstallMonths_Change()
On Error GoTo Err:
Application.ScreenUpdating = False
Sheet1.Cells(1, 1).Select
Select Case Sheet1.cboInstallMonths
Case 1
Call FourWeekMonth(1)
Case 2
Call FourWeekMonth(5)
Case 3
Call FiveWeekMonth(9)
Case 4
Call FourWeekMonth(14)
Case 5
Call FourWeekMonth(18)
Case 6
Call FiveWeekMonth(22)
Case 7
Call FourWeekMonth(27)
Case 8
Call FourWeekMonth(31)
Case 9
Call FiveWeekMonth(35)
Case 10
Call FourWeekMonth(40)
Case 11
Call FourWeekMonth(44)
Case 12
Call FiveWeekMonth(48)
End Select
Range("A1").Select
Err:
End Sub

Sub FiveWeekMonth(intStartWeek As Integer)
Sheet1.Cells(8, 4) = intStartWeek
'unhide 5th week column
Columns("T:W").Select
Selection.EntireColumn.Hidden = False
'hide 4 week total column
Columns("Y:AB").Select
Selection.EntireColumn.Hidden = True
'unhide 5 week total column
Columns("AC:AF").Select
Selection.EntireColumn.Hidden = False
'Columns("S:U").Select
'Selection.EntireColumn.Hidden = False
Range("A1").Select
Sheet1.Cells(8, 29) = VBA.MonthName(Sheet1.cboInstallMonths, True)
Range("G,K,O,S,W,AF,AK").ColumnWidth = 8
Call basPublic.InstallsSize5Week
booWeekType = True
Range("A1").Select
End Sub

Sub FourWeekMonth(intStartWeek As Integer)
Sheet1.Cells(8, 4) = intStartWeek
'hide 5 week column
Columns("T:W").Select
Selection.EntireColumn.Hidden = True
'unhide 4 week total column
Columns("Y:AB").Select
Selection.EntireColumn.Hidden = False
'hide 5 week total column
Columns("AC:AF").Select
Selection.EntireColumn.Hidden = True
Range("A1").Select
Sheet1.Cells(8, 25) = VBA.MonthName(Sheet1.cboInstallMonths, True)
Range("G,K,O,S,AB,AK").ColumnWidth = 8
Call basPublic.InstallsSize4Week
booWeekType = False
Range("A1").Select
End Sub