Function module to count periods elapsed

Hi SAPients!

Is there an FM to get the number of periods elapsed counting from one date or period.

Example:

If I send as parameter 200207 or 20020701 the FM should return 36, because 36 (monthly) periods have elapsed since then.

I tried SE37 but I can´t find the right one.

Or... do you know other way to do this?

Thank you.