Modify a parameter field value

Hi,

Is it possible to modify a parameter field value after user's input in CR 2008 by using a formula?

I'm trying:

{?[!V000036]} = "[CALMONTH].[200905]" and

{?[!V000036]} := "[CALMONTH].[200905]"

but none is working.

Is it possible in any other way?

Thanks and best regards,

David.