EnableCalculation Property [Excel 2003 VBA Language Reference]
True if Microsoft Excel automatically recalculates the worksheet when necessary. False if Excel doesn't recalculate the sheet. Read/write Boolean.
When the value of this property is False, you cannot request a recalculation. When you change the value from False to True, Excel recalculates the worksheet.
This example sets Microsoft Excel to not recalculate worksheet one automatically.
Worksheets(1).EnableCalculation = False