Taking the active pills should stop it, especially if you have a window of a few days to let them take effect.
On a side note, I find that having sex both when I'm expecting my period and when I want it to end makes it happen, like clockwork. If I am done with my active pills and am awaiting the start, I have sex and, bam, the next morning I have my period. After a few days when it has died down again, same thing, I have sex and it's completely done. Wonder why that is?