As per title, was wondering if anyone knows how i can modify the "skill" requirements for any school-dependent (non custom) spell to be successfully cast;

Per UESP wiki:

Chance of success is (Spell's skill * 2 + Willpower / 5 + Luck / 10 - Spell cost - Sound magnitude) * (0.75 + 0.5 * Current Fatigue/Maximum Fatigue)

That "spell's skill" right there, where does the ignorant peon (me) find it pretty please? In detail please, my CS skills are pretty rudimentary.

My apologies if this is dumb/too superficial a question, but honestly i gave up looking this up in google..nothing even close to a hint.

Any help would be trully appreciated

edit: in the off chance this helps, what i want is to raise (significantly) the difficulty of casting bound weapons and armours spells. Am not asking about altering their base magicka cost.

Spell's skill refers to the Skill corresponding to the Spell. For example, for the spell "http://www.uesp.net/wiki/Morrowind:Alteration_Spells#Jump", Spell Skill refers to Alteration.

Also, you cannot modify formulae in CS, its hardcoded. Alternatively you could change GMSTs. But I doubt there is a way to make a spell harder to cast without changing its cost.