Parameters with a union statement

I have a report that is using a union statement to pull in data from two identical tables except that one is for current month, the other for archived data.

What I want to do is prompt the user once for a date and use the value to select from the right table. Since a sales date can only exist in one of the tables, one union will work, the other not.

But the report in prompting me for a parameter for each query....which is in Informix and the prompt is this: "?"

Is there anyway to force both halves of the query to see this as one parameter so the user is only prompted once?

Thanks

Have you tried to use this sql structure

="select * from table_1 where Sale_date = '" & format(Parameters!date,"MM-dd-yyyy") & "'"
union
select * from table_2 where Sale_date = '" & format(Parameters!date,"MM-dd-yyyy") & "'"

|||

Can I do this in the data set?

Thanks