Worksheet.EnableFormatConditionsCalculation (Excel)

Returns or sets if conditional formats occur automatically as needed.

When set to True (default), evaluation of conditional formats occurs automatically as needed. When set to False, conditional formats are not re-evaluated. Any previously applied conditional formatting will still be visible, but it will not update as cell values or AppliesTo ranges are changed. The purpose of this flag is to allow VBA programmers to configure a rule completely before evaluating it. This is particularly useful when condition is applied over a large range because performance can be slow in these cases.

ActiveSheet.EnableFormatConditionsCalculation = True