Reporting Services :: Division By Zero

My function in my report, thu function I currently use is the following:

Public Function CalcDivision(ByVal Numerator As Object, ByVal Denominator As object, ByVal DivideByZeroDefault As Object) As Object
If Denominator <> 0 Then
   Return Numerator/Denominator
Else
   Return DivideByZeroDefault
End If
End Function

=Code.CalcDivision(Fields!Sales_Refund.Value,Fields!Sales.Value,Nothing)

The problem is that it still return zero instead of nothing, which is the goal here, I have tried different variation but still returning zero.