keyboard key hold program

i have a friend who is quaderaplegic and he has to use the mouse with 2 closed fist and we play an online game called dark orbit and he is realy good but the problem is is he cant fire rockets because that requires you to hold down the space bar. so im looking to find kinda the opisit of sticky key where he would just have to hit it 1 time and it would be down until he hit it again witch would release it