SSRS "If - then - else" formula #error

You can modify SELECT:

-- Test data
DECLARE @t TABLE (val1 Int, val2 Int);
INSERT INTO @t VALUES (10,0),(20,0);
SELECT * FROM @t;






SELECT Sum(val1)/Sum(val2) FROM @t;

Msg 8134, Level 16, State 1, Line 6
Divide by zero error encountered.

;WITH cte (p1, p2) AS (
   SELECT Sum(val1) AS p1, Sum(val2) AS p2 FROM @t
)
SELECT CASE WHEN p2=0 THEN 0.0 ELSE p1/p2 END AS pp FROM cte

(value / "divide by")  has "divide by" zero error ( or more formally )
(numerator / denominator)  has divide by zero error

You need to test if the denominator is zero (your existing formula tests the numerator)

=iif(sum(Fields!Calculated_Revenue.Value) = 0, 0,
sum(Fields!Calculated_Inv_Margin.Value)/sum(Fields!Calculated_Revenue.Value))

note: you also need to test the summed value, just like you have used in the calculation

So I tried the following:

=iif(sum(Fields!Calculated_Revenue.Value) <> 0, sum(Fields!Calculated_Inv_Margin.Value)/sum(Fields!Calculated_Revenue.Value),0)

This Produces the same result:




I tested the value by using the following:
=iif (Sum(Fields!Calculated_Revenue.Value) = 0, 0, 1)

This returned the result I expected:

I don't understand it - it seems like it is re-evaluating the formula after "then" in the if statement.

I also tried this:
 =iif (Sum(Fields!Calculated_Inv_Margin.Value) = 0, 0,
sum(Fields!Calculated_Inv_Margin.Value)/sum(Fields!Calculated_Revenue.Value))

I'm going to try and store a formula with the 0 result to see if I can make it work that way.  

Can you do a case statement in SSRS formula editor?  

Thanks!