Play panel tempo setting.

My issue is with the tempo setting in the play panel and setting a tempo for my file when converting to MIDI. When I am composing, if I change the tempo in the play panel and then save as a MIDI file, once I open the file, the tempo is insanely fast. There seems to be no way to change the tempo without affecting the percentage setting. For example, I would like my piece to be saved at 80 bpm, but changing the tempo on the play panel also changes the percentage, and once saved the MIDI plays back at 120 and that is not what I want!
Someone please help me.
Thanks