Hmm, you might want to have a window pop up, asking how much you want to withdraw/deposit/donate into the bank/other players pockets. Sadly, i dont know anything about making custom DeusEx windows(Like the Keypad ones, not the ones you can climb out )
Prehaps you should PM [A]lex or [A]Nobody, and ask them for a basic makeup for a custom window for this kind of thing, it might help you make better mods too