I believe you are referring to "automation" which has been discussed here before..  In short, right click on the parameter that you are wanting to affect and click "Create Automation Clip".  This will create a adjustable line in the playlist that you can adjust.  Just play with it and you will get it in no time.  You could also go the route of actually recording the changes live, but i find the graphical automation clips much more accurate and easy to control.