Inducing Early Period?

I have a weekend trip coming up in about three weeks, and that's exactly when my period is supposed to be, and I really don't want it to ruin the romance.  
Does anyone know any way of making my period start before/after the trip? Preferably that doesn't cost a lot or require a doctor visit. 
I've heard parsley tea can help, but I don't know exactly how to use it for this lol.