If the portal of dates is for display purposes only, or as a list of dates from which the use can choose, you might be able to use a virtual list. A fairly simple ExecuteSQL statement could return a list of unique (distinct) dates matching the Doctor & Location values. The SQL would, of course, need to be triggered by something, such as OnLayoutEnter or OnObjectModify applied to the Doctor and Location fields.
It's really just for display purposes only, so the user knows the days the doctor will be in for clinics.
I'll have to do some googlingon SQL, I'm not familiar with using it yet.
Thanks very much.
You will want something along the lines of:
Select Distinct clinics::date_field From clinics Where clinics::doctor = ? and clinics::location = ?
You will find that ExecuteSQL returns date values in this format: yyyy-mm-dd. You can alter this behavior with use of the Coalesce function. see tip #2 on this blog entry for a better explanation: