MAME "not" key

[EssexMame]

Hi
I'm sure it's possible, in fact I think some keys are defined by default (e.g. A NOT SHIFT) but how do I define a key in mame to be for example "press Key 5 but not when Key 2 is pressed"?
i.e. 5 NOT 2

I want 2 AND 5 to be COIN for player 2, and it works, but it also adds coins for Player 1 as the 5 key is of course pressed.

Basically, I want Gauntlet to allow my single coin button to add coins to player 1 by default, but ONLY to player 2 if P2Start (2) is held when coin pressed.

[romshark]

To set a NOT in MAME, simply press the key twice when setting it. So for coin 1, press 5, then press 2 twice.

Just tried it in a game on my "testing" MAME on my normal PC.

[EssexMame]

Perfect, and so simple once you know how - thanks a lot!
I could not find that ANYWHERE (though it's not an easy search string to do)