re: Cold sore remedies...any way to stop one once it has already gotten going?

Starting taking acyclovir last night and I'm rubbing some prescription topical cream on it as well but it's early and hard to tell if it's going to stop it from blistering or not. Never had any luck stopping one from blistering once it's flared up. Sucks because I'm meeting a chick for a 4th date tonight. The sore doesn't look bad yet but it's to the point you can tell it's a cold sore if you look close enough.