Can you make the F-keys flash?

Is it possible to make the F keys act like a flash button? I would like to add a blackout and a fixture group 100% intensity button. Currently just assigning a preset to them, but then I have to have another preset to turn them off. Ideally I would like to just hold the F key for the desired function, then it turns off once I let it go. Exactly like how the flash button works on override cues. (My workspace is already at 20 faders, so I am trying not to spill over to a third bank)