SSRS Expression IIF Zero then ... Got #Error


Need some help for SSRS.
The column % expression is
=iif(sum(Fields!ColumnA.Value) = 0 or sum(Fields!ColumnB.Value) = 0,0,sum(Fields!ColumnB.Value) / sum(Fields!ColumnA.Value))

But I am getting #Error if ColumnA is zerro and no error if ColumnA and B had no value. Please advise what is wrong with the expression.

There is nothing wrong with your expression but there is something wrong with SSRS. You have to check twice if you want to pass the validator:

iif(sum(Fields!ColumnA.Value) = 0 or sum(Fields!ColumnB.Value) = 0,0,sum(Fields!ColumnB.Value) / iif(sum(Fields!ColumnA.Value) = 0,1,sum(Fields!ColumnA.Value)))

Thanks RogierPronk,
What do you mean by check twice? How do I check twice?
Thanks again

Thank for the hint RogiePronk. The following works.
=iif(sum(Fields!ColumnA.Value) = 0 or sum(Fields!ColumnB.Value) = 0,"", sum(Fields!ColumnB.Value) / iif(sum(Fields!ColumnA.Value)=0,1,sum(Fields!CalumnA.Value)))