how long does it take dulcolax to wear off.?!

I was constipated the other night and my mom bought me dulcolax to help. After a few mins i went to the bathroom and it was all fine. Today during school though, I had bad direah and i cant eat anything because i poop it right out. Me and my friends are going to the movies tonight around nineish and i was wondering if it could be worn off by then beacuse i do want to be able to eat while watching the movie. I am fourteen and took two pills. Thanks.