Hi Tony, here are some steps.

First start by selecting this face from your object:



Do an invert selection, and then Delete, to get just this piece by itself:



Next select one edge on one of the panes. By selecting one edge you set the window selection to target edges.



Then do a window select like this to select the other edges:



Note that I selected from left to right here. Starting from the left and going towards the right will only capture things strictly inside the window. This kind of selection window will show with a solid outline (for the rectangle itself I mean). If you go starting from the right and going towards the left it will instead target anything that intersects the window even partially which can be good in different situations. That "crossing window" shows up as a dashed window outline instead of solid outline.

Anyway, that is the quick way to get all these pertinent edges selected.

Now do a Ctrl+C to copy the curves of those edges to the clipboard, then hit Delete, which will "untrim" the surface and remove these holes to recover the underlying surface. That will produce this now:



Now do Ctrl+V to paste in the curves, you will have this now:



Clear the selection and select just the main surface:



Run Edit/Trim and select the curves as the cutting objects. Then you will still be in the Trim command and it will ask you to pick which pieces to discard (or which to keep if you flip the mode) or you can hit Done/right-click there to keep all pieces if you want.

In this case select this outer piece to discard:



And then that should produce your window panes:




I think that is what you were trying to do, but let me know if I didn't understand correctly.

Basically this is getting into some of the surface-level modeling tools instead of the solids modeling tools.

Hope this helps!

- Michael