>It works (just put the M in the Format property, and Option1,Option2,Option3 in InputMask), but it's actually far better to use anything else - dropdown combo, listbox, or even an optiongroup (not this time - you obviously have scarce real estate). The trouble with @M is that it's counterintuitive, and it doesn't provide for a visible list.

Good explanation - I was thinking along those lines too, but not as coherently as you :)