Changing Field Value With Parameter

Hi,I'd like to change a field value in my main data source query using a parameter. I cannot figure this out.I'd like to be able to use a parameter to change the field 'DueDays' to 'AgeDays' and vice versa if I choose. I would specify my parameter values as the coordinating field names which are;AgeDaysDueDays[code="sql"]Select Last,First,SiteName,DueDays From My Table[/code]Seems like such an easy thing to accomplish but apparently not for me. Thanks