GURPS version of Ghostly Reload D&D spell?

[thom]

So the crossbow-wielder in my PCs group wants a GURPS version of the 3.5 D&D spell that does this:

"...After the wielder shoots a projectile from the crossbow affected by this spell, the magic immediately cocks the crossbow so that the weapon can be loaded again. This spell pulls the string of a hand crossbow or light crossbow into place once per caster level (maximum ten times at caster level 10th) and the string of a heavy crossbow into place once per two caster levels (maximum five times at caster level 10th)."

With GURPS, I can see limiting the number of times a crossbow is cocked by Magery level, and the spell takes one second to cock the crossbow each time. My main questions for the groupbrain are:

• does limiting the spell by making it Very Hard vs. Hard to learn matter?
• ditto for adding the High skill does not reduce this spell’s cost language
• what about making the Time to Cast the spell be 2 seconds (vs. one)?
• and most importantly, exactly how much FP should this spell cost?

I'd appreciate any insight; thanks!

thom