Dynamic population of a selection parameter in a Variant

Hi All,

Is there a way to dynamically populate the selection-screen parameter(not a date) in a variant...SAP provides option of doing this only for dates(FM RS_VARI*).

To explain my requirement,

I have 3 parameters on the selection screen. Eg: In the variant if param1 = A and param2 = B. Can I write a function to read the two parameters above and populate param3 dynamically.

TIA & Regards,

Pramod