Kent Elrod demonstrates a method using object snaps (osnaps) in AutoCAD that allows users to snap to objects that are being moved.
"You can osnap to an object even if it is in the selection set. If you have two parallel lines and you want to move them the distance between the two lines, start the Move command and pick both lines, use an osnap for the first one, say endpoint, then use the Perp osnap command and grab the second line. Even though the lines are in the selection set you are able to use them as references."
Notes from Cadalyst Tip Patrol: When AutoCAD executes a command, nothing is changed until the action is complete. Therefore, when you move objects, the objects selected to be moved are not moved until they are moved. (No, that’s not doublespeak, it's just confusing.) This means that users can snap to objects of a selection set even though they are the objects being altered. They won’t be altered until AutoCAD is told how to alter them, so they are still in their original position until the Move command is over.