I often use the standard $widget->pack() syntax with the -fill='x|y|both' param to achieve some level of resize control. I have read (From "Learning Perl/Tk") that the place widget manager might be better for fine grain control. Takes a little more work though to get the params right.
Hope that helps a little,
As the above posters have mentioned, an example would lend to a more precise solution:)
-ase