|Excel Developer Reference|
Version Added: Excel 2007
expression A variable that represents a Worksheet object.
When set to True (default), evaluation of conditional formats will will occur automatically as needed. When set to False, conditional formats will not be 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 as performance can be slow in these cases.