avoiding "NaN" , "infinity" in reports

When I use calculation in generating reports, I get "NaN" and "Infinity" values, I wanted to avoid this and display "0" if the result of calculation is null or infinity..

I used the below calculation

=(Fields!approved_tier_cnt.Value)/(Fields!approved_cnt.Value)

Please let me know how to avoid "NaN" and "infinity", while displaying in reports

Regards

Durai