I want my Alt button to fire and change sensitivity temporarily until the key is released.

1) press Alt
2) fire + change in sensitivity, e.g. 0.8
3) release Alt
4) fire stops + change back to original sensitivity, e.g. 1

Can it be done? No?

EDIT: I think I got it

alias +l33tacc "sensitivity .89"
alias -l33tacc "sensitivity 1.0753"
bind ALT "+attack; +l33tacc"