Casting Light Spell

I play primarily with the mouse, and I'm not a fan of having to find my alt key to cast the light spell on my Avatar instead of my pet. Sometimes I hit the flag key next to the Alt key and the game minimizes. Pet heal now casts only on the pet, but not so for Healing Touch. I've mapped dual keys for Alt + the number to a mouse button to heal myself, but I'm running out of mouse buttons to do the same for the light spell. Can we make the light default to our Avatar?