tempo micro adjust with remote override mapping

[owlis]

Hi I have a song that plays at 100bpm which needs to play in sync with a completely independent sound source also at 100bpm. How can I micro adjust the tempo with a controller (not using the mouse) either plus or minus the current tempo. ie momentarily set the tempo to 99.5 bpm or 100.5 bpm depending on whether I want to speed up or slow down reason till it is in sync with the separate sound source and then bring it back to exactly 100bpm once the tempos are locked.

Any ideas?

Cheers
Pete