I took a bound dagger (0 weight) and with an grand soul gem, enchanted it thus:

Capture Soul 1 second on strike
Shock Damage 15 points on strike
Weakness to shock 100% for 1 second
Weakness to magic 100% for 2 seconds

Now if I'm right, the extra second of magic weakness means that with each consecutive blow, this should have a devastating effect as the 15 shock damage should multiply exponentially. Am I correct? It gives me 33 uses.

Slay thy might beasteth witheth thoueth dagger dubethd by meth, "Phil."

The weakness to shock will only apply to the next strike, and it doesn't stack. Each strike will cancel out the previous one. The weakness to magic will stack, but with each one lasting only 2 sec. You MIGHT be able to get it to stack 3-4 times.

Increase the weaknesses to 3 secs and reduce the shock damage to 5. After 5 strikes, you should deal 80 damage, the next should do 160... etc etc