you can only select at the beginning of report or a subreport. You cannot request additional information once you have selected your data.
I took me a week to figure that out...10 years ago.
Best solution is a stored proc, but that doesn't look like a very good option...if they don't have SQL Server, then I would guess that don't have a system that supports stored procs.
How else to get around this...
you could use command object to select related pieces of data and link to the new tables.
sub reports (not recommends as it will generate a lot of hits to the database, but it is a way to requery the database)
nothing else really comes to mind
HTH