Meinst du es so:

if (key_space == 1) // if we press the space button
{
ent_cycle("jump", my.skill22);
my.skill22 += 5 * time_step;
wait (-1);

if (jumping_mode == 1) {
(z_force > -20) { z_force -= 3 * time_step; } ELSE { z_force = -20; }
}

if (jumping_mode == 0) {
if(z_force > -20) { z_force -= 3 * time_step; } ELSE { z_force = -20; }
}



} //end if


} //ende action