Okay so im a nord, nords have 50% frost resist, but i want to get my spell reflection up. So if i make an enchantment that makes me weak to frost by 50% will that take away the resistance and make my spell reflection work better on frost?

I'm pretty sure reflect applies before resistances, meaning there is no need to do this.

This means that your reflect first checks to see if it was successful. If not, then your resistances check to see if your resisted the damage. This way you aren't penalized for having large resistances.

Resist magic comes after absorption and reflect. Read http://www.uesp.net/wiki/Oblivion:Magical_Effects#Reflect_vs_Absorb_vs_Resist about it

Ah, that will work even better thanks guys

Remember that 50% resist + 50% resist = no damage. 50% resist + 50% reflect/aborb = half the damage, half the time. On the other hand, if weakness to frost is thrown at you (and I'm not sure if anything will do that), your resistance would always drop if that's all you have, whereas you get a chance to reflect or absorb that spell with the mixture.

IIRC the weakness spells do appear in leveled lists of spells that enemies can have, but the random nature of the lists means that they will rarely have both a frost damage and a weakness to frost available. They may be using a weapon with both enchantments, to which your defense is staying out of range!

Which is why Bretons with Mundane Rings are so popular.