This feature can be used to conditionally enable the expression.
Check out the What's New in QlikView11 demo app (e.g. download from the QV demo site), on report tab, there is a demo of that feature (and looking at the expression used in the conditional field, it should be easy to understand).
Hope this helps,
Thanks for the advice. Can you use the Expression Calculation Condition to manipulate the calculation order?
Or Condition: Column(1) >0
That would help me to create a Chart with very complex Expressions. The condition should not recalculate the Expression_1 again
Oderwise it will crash.