Thanks that worked perfectly. Qlik Sense gives an error on the expression but will execute with the correct answer anyway.
Thanks for the help.
Here is the final expression:
alt((above(Exponential))*exp(-.6/12),(Sum([Static Raw Value])/Sum([Static Number of Sites])/Sum([Static Number of Days In Month])))
FYI, "Exponential" is the name of the column that this expression resides in.