[Dennis]

Hi Merrie,

There are a few ways to do this - the first one that comes to mind would be to use the built-in Boolean->Knife tool. You can create a second box that intersects your original box where you want the cuts to appear, then select the original box, then select the "cutter" box, then finally select Object->Boolean->Knife. In the screenshot I attached, the "short" box is the cutter box.

Good luck