Sadly that won't work: Calculation mode is set for all the worksheets
in all the open workbooks, so when you select another sheet
calculation mode will be set to automatic and ALL the sheets will ne
calculated.

You would have to do something like this:

Set Calculation to Manual.

in the Thisworkbook module add this

Private Sub Workbook_Open()
Application.Calculation = xlCalculationManual
Worksheets("SumproductSheet").EnableCalculation = False
End Sub

and in the SumProductSheet module add this

Private Sub Worksheet_Activate()
ActiveSheet.EnableCalculation = True
Calculate
ActiveSheet.EnableCalculation = False
End Sub

regards
Charles


Private Sub Workbook_SheetActivate(ByVal Sh As Object)
If ActiveSheet.Name = ("Sheet1") Then
Application.Calculation = xlManual
Else
Application.Calculation = xlAutomatic
End If
End Sub