You can say "I will not stay in a sexless marriage" or you can say "I'll be having sex with you 3x a week. You, of course, know where the door is if you don't like it."
I don't think the latter is possible without consent of the other person MJ. You can't exactly force someone to have sex with you, especially us females. It all comes back to attraction....or something....you need to find what gets each other's juices flowing. Both ways, not just one way. LFL