Rewire tempo change automation on a budget?
I'm making an attempt to use Reason's Redrum rather than buying an outboard drum machine, only to find that our band happens to have written quite a few tempo changes, which reason doesn't support. After doing some research I learned that you can use Sonar Cakewalk to automate tempo changes through Rewire. This method works just fine and dandy on the desktop we have in the studio, however my laptop doesn't have quite enough memory to run Cakewalk and Reason simultaneously without locking up in play mode indefinitely (I.E. I press stop and nothing happens). I can't haul the desktop around to shows, I don't have any money to upgrade my laptop. Is there a rewire device that's only function is to automate tempo changes, or any piece of software that is less memory intensive than Cakewalk or Ableton that I can use to automate tempo changes?
Any other ideas to solve my problem?