Thats is one really easily. You just highlight the "track line" and right click the BMP thingy, and click "Create automation clip". That creates a new thingy down on the second sequencer-thingy (the one where you can scale clips/sounds). You then move the points on that thingy to make a downhill slope, or uphill (you can also add points to it to make zig zags, or whatever).
Really bad explanation, but I learned it off of youtube.
http://www.youtube.com/watch?v=mTE50HexkKI
Now. Feedback on the song?