After a +2 Evasion Boost, Blizzard will have a 42% chance to hit (.6 x 70).
Blizzard has a 10% chance to freeze the target.
There is a 1/16 chance in Gen 5 for a Critical hit to occur.
Multiply these and you get 21/8000 or a .2625% chance for Blizzard to hit, Freeze and critical hit on the same move.
If you want the chance for the entire battle, please comment.