Vishal,

You want workbook to calculate only when your Sub CALCULATION() Runs.

Put this sub in ThisWorkbook CodePane for every workbook you want to force CalculationManual

[VBA]Sub Application_WindowActivate(ByVal Wb As Excel.Workbook, ByVal Wn As Excel.Window)
Wb.Application.CALCULATION = xlCalculationManual
End Sub[/VBA]