Duplicate the Infestor - Infested Terran mover (basically what it uses for launching the egg thing), then modify the various fields and experiment till you get what you want.
In order to use this for the attack, however, you must change the effect to a "Launch Missile" effect and change the field Impact Effect to whatever effect your weapon has. Change the ammo unit to some kind of dummy projectile, then add in the mover from the above section to it.
EDIT: Also, the Arc and Arc Slop fields only edit where the unit can target things, not the missile arc.