I've been practicing to a metronome for once this evening, and I realized in one of my band's songs, there's a significant slowdown, and there's no way I can turn the dial on my metronome in between the parts. Is there a program that can control the tempo of a metronome for me, and I can set it to change at a specific time in the song?
i don't know but it is a good question so bump for ya.

my only guess would be that you would have to have one that either takes MIDI but more likely does it on it's own. In otherwords, you set the placement and time changes and it changes for you and then back. Although I have zero experience doing this. Good luck.