Suggest Medication To Pre Pone Periods

Hi doctor... I have a function at home on 21st feb ..... My period lie between 17 to 19 i have taken regestron for prepone my periods i.e, from 14th to 17th feb (3tab each day). I get very regular periods..... I don t have period tilll now..... I a dilemma...... Need to get my periods by 19th night..... Willl i get the cramps ..... If no suggest me