How can you "null" a zero balance?

I'm trying to "null" zero balances on a report in order to calculate the median price.

I did the following:

1.) Placed and suppressed the field "sold price" on a listing report which listed ALL "sold prices"-  let's say 100 sales

2.) Created and placed on the listing report a formula:

   If {sales.sold date} in date (2015,04,01) to date (2015,6,30) then {sales.sold price}

This formula lists, let's say 20 sales from Q2 2015 and a $0 for the 80 non Q2 2015 sales

If I calculate the median sale price, I get $0 because of the 80 $0 balances.

Thus, I need to "null" the $0 balances with an else command in my formula.

Any assistance would be greatly appreciated.