Ok I'm working on a mod in an attempt to make the Vampiric Drain spell give the player destruction magic experience to boost the destruction skill. So basically I want to be able to kill stuff with Vampiric Drain and improve my destruction skill at the same time. Atm this spell is worthless and it is very weak and doesn't improve any skills while using it. Any help would be greatly appreciated.

What would I have to mod in the creation kit to make this happen?

I think you are mistaken, It does increase your skill rate, just not very fast.

All you have to do is go to the spell and see what magic effect it uses, then open that up and you will see under magic skill that it uses destruction. If you want it to increase the skill faster change the "skill use mult"

Are you sure? I just checked in the creation kit and am having a hard time finding the magic effect for vampiric drain 1-4. As far as gaining experience the magnitude must be set at 0.00 because I used vampric drain for about 30 minutes straight and my destruction skill bar did not move at all. I switched to flames and and boosted my skill by 2 points in about 5 minutes.

I just looked, my copy boosts destruction. The effect depends what stage of vamprism you are, but the first one PlayerVampireAbsorbHealthConcAimed is a dest skill with a skill use of 1. Flames uses FireDamageConcAimed with a skill rate of 1.4 so set it to that if you want it equal to flames. I'd guess you have a mod that changed it or something or your not looking in the right place.

I just changed the PlayerVampireAbsorbHealthConcAimed to 1.4 and still no gain. Do you have a vampire character to test it on?