You can't detect the closing of the queries from within the form--but you should be able to clear the text boxes right after you've opened the queries and passed the data to them.
But if the queries are grabbing the values from the text boxes (using Forms![form name]![text box name]), you won't really know when the data's been grabbed, will you? I'd suggest that you just clear them 1 or 2 seconds after the queries have been opened. That should be enough time for the queries to get their data.
To get this to happen after 1 or 2 seconds, modify your command button Click events so that after they open a query, they set Me.TimerInterval to 1000 (or 2000 for 2 seconds). Then create a Form_Timer event procedure as follows:
Me.TimerInterval = 0
Me.Text1 = ""
Me.Text2 = ""
I think that will do it. Rick Sprague