IIF and IsNothing with SSRS Expression

SSAS and SSRS
1

Please forgive my ignorance, I need help with returning a 0 from my lookup value versus it currently returning a blank space in my SSRS report.

=Lookup(Fields!InsuranceCarriersID.Value , Fields!InsuranceCarrierId.Value, Fields!TotalBalance.Value, "InsAgingSubReport")

2

How about:

IIF(IsNothing(...your original expression...), 0, your original expression).

If you don't like the duplication (I don't) consider writing a custom function.