Putting a hole in a patch is not possible, however, in DoomEd you can select the patch and export it to obj. Afterwards you load it up into milkshape3D, remove the necessary polygons, and then export to lwo. Then you load it up into your map. If you don't have milkshape or whatnot, it's probably easier to make 4 patches instead, thus you'd have a hole in the middle.