Yes, there is a way. Set your tempo in the transport to where it should be. Then under the global Options menu at the top, go to Tempo ---> Export tempo information to audio file. I think that should do it.
cool thanks for the tip!!
strange that they not let us able to manually insert that value directly on the detect tempo window.
I had to do a continuous mix and i was in a hurry so i've done it in Pro-Tools, i'm still a real noob in PT (third time i use it), but i've found all the things very easily, as it happens very often, in logic things are more trickier than it should