WinArrange arranges the last two activated windows on your screen. If you arrange horizontally it will put the last activated to the right and the previous window to the left. Respectively it arranges the last one on the top and the previous to the bottom if you arranged vertically.
It's also possible to select windows from Drop-Down-Lists, arrange them and save this arrangement in different Memos. So whenever you want to arrange exactly this window pair you can do that with one click.
Give WinArrange a try to see how useful it can be to help you manage your open windows.