Jeffrey

 Thanks for the response. I didn't really find the msdn documentation on
IListSource very helpful. It read like it would be helpful if I already
understood how thing worked!  In any case I found a simpler way. Since in my
case there are a fixed number of cells in the matrix I ended up just using a
panel with 81 TextBox controls -- generated and placed at form load time. I
used the Observer Pattern to link up my cell objects with the corresponding
TextBox so that any change to the value of a cell would be reflected
immediately in the UI.

 Interestingly I found that letting my app run full speed resulted in no
update of the UI, presumably the messages were being genereated so quickly
that each message caused the previous to be ignored.  I vaguely remember
something about this message loop handling from some long ago reading about
Windows architecture. What I wanted to achieve was a visual reflection of a
game board tree search for the game of Sudoku. I finally got it to work by
inserting a call to Sleep() in my cell update code.

 One problem remains however. When the form is running you can watch the
tree search progress (and regress), but if I bring another application's
window in front of the form, then switch focus back to the form I find that
the visual update has stopped. Any idea what might cause that?

Thanks,
Bill