using alt as a shortcut key/list of symbols for shortcut keys

What would be a "code symbol" for the Alt key that I can use as a shortcut to link a sub to? For example Shift Key is "+", Control Key is "^" in the following assignment:

Application.OnKey "+^1", "sub_to_run"

What about the Alt Key?

Also, is there a source on the web/link anyone knows of that lists all keys of the keyboard and their symbols that VB would recognize, and that I can use as a shortcut to trigger subs from?

Thank you