calculate average values excluding rows with 0 values

Suppose I have the following column in a report like this:

2

3

0

4

0

at the bottom of this column, I want to add the average value. The average function in CR gives 1.8 of above data (because (2+3+0+4+0)/5 =1.8) . What I need is (2+3+4)/3=3 I want exclude all 0s when calculate average values. How can I do that in CR?

Thank you!