Huh? I hope this is a fixed gear. If so you're fine, and you don't need a rear brake. Otherwise, not good! Why can't you put a rear brake on? If this is truly the case I would:

a) Get a different frame
b) Not ideal, but you could get a disc/canti fork and run one of each on the front, activated by different levers.

I cannot recommend trying to control one brake by two levers. Seems like a terrible idea.