How to use the alt key as an override key

[fmath]

I want to use the alt key in conjunction with other keys to toggle on and off
osnaps. I know I can set osnaps to come on automatically but I would rather
have a single osnap come on only when I want it to without other snaps lighting
up the drawing.

When I was using autcad I had a program that worked with it so I could
program alt e to enable endpoint. Whenever I hit alt e the endpoint box
would light up on an endpoint. Same with the other keys.

I know about mouse gestures but I want to use the right mouse button
to repeat the last command.

I tried using the customize part of tools but the alt key seems to
be set to click on menu choices.

Any ideas?
Thanks