SSRS Formula or expression to change NaN to 0

Question

I am using the following expression to work out a percentage:

=Fields!Days.Value/Sum(Fields!Days.Value, "Date_month_name")

Days.Value is showing as 0 however in a few of my results instead of reading 0% in my percentage column it is actually reading NaN (Not a Number).

Does anyone know the exact expression forumla i need and where I should paste it in my current expression to say "Where NaN is showing, put a '0' instead?"

(See image)

Answer 1

How about

=IIF(Fields!Days.Value > 0,Fields!Days.Value/Sum(Fields!Days.Value, "Date_month_name"),0)