Sometimes, you need to change the BACK_COLOR of a cell, based on the result of an evaluation, such as 'Change color to YELLOW if Condition A is TRUE'. But what if you don't want to change the BACK_COLOR if Condition A evaluates to FALSE (and leave the back color as it was)? Surprisingly, the answer is quite simple... Just set it to NULL.
For example, change the BACK_COLOR to Yellow if the flag 'NewFact' is greater than 0, otherwise leave it alone:
BACK_COLOR(this) =
IIF([Measures].[NewFact] > 0
, 65535 /*Yellow*/
, NULL /* Don't do anything */) ;
Very clean, simple and it won't mess with any pivot table formatting theme you might have chosen.. I love it!