Bind the command to SPACE instead of LMOUSE.
What I'm trying to get at is that if someone wants a secondary weapon, then your mouse has both of those weapons bound to it. For example: You put a rocket launcher and a machine gun on a fighter jet in two slots. When you click once, though, there is a rocket coming out AND a spurt of machine gun fire.
I'm thinking maybe that there could just be a separate script called, "ShootOnSpace" or something. Or a copy of the same script within the original remapped for the space bar or some other key.