Formula for % chance amt won is consistent with a given winrate

[AliasMrJones]

I know the formula for determining RoR and for calculating max win/loss after n hours for a given confidence %. But I'm having trouble trying to go the other way.

A good winrate online is supposed to be 2 BB/hr. with a standard deviation of 15.

After n hours of play a player has a profit/loss of x. What is the formula for computing the % chance that this player is the player above (or at least over the long run has/will have the stats of the player above)?