Cell displays #Error when I expect an INT in SSRS

I'm having a problem when t开发者_JAVA技巧rying to display a 0 when there is an occurrence of a special which I have listed in my data source

The normal sum computes fine and displays in the cells without the special day, but the cells which have a special day displays an #error

=iif(Fields!SpecialDay,
0,
Fields!NormalSum)

and then I have tried variations to get the integer, such as

CInt("0") Fields!NormalSum - Fields!NormalSum

but I still get an #Error in the cells for which I wish to display a 0.

Any thoughts on this particular problem?

Many thanks

Ending up using

=iif(Fields!SpecialDay,
nothing,
Fields!NormalSum)

Better to do so in VB.

The problem is you are referring to the object Fields!NormalSum You need to refer to its "Value" property Fields!NormalSum.Value