Can I keep a cold sore from scabbing over?

I have a formal event in 2 days and I have a cold sore right above my lip. I have been treating it since monday (4 days ago) with lysine and even took a round of valtrex that my family memeber keeps onhand for cold sores. It has condensed into a big whitehead and looks as though all of the infection is just sitting at the top. It isnt really painful, but I dont want it to scab over. What do I do?!