Alright, go to Insert 1 on the mixer and add Battery 3 as a VST. Select the kit that you want. Now, if you look at the Insert 1 right below the volume, there's a "FX" light, and there's a floppy disk beneath it. Click on the floppy disk, choose where you want to save your audio to (name it after whatever part you're getting ready to record), and proceed with recording the way you normally would. Before you do this, however, make sure you're in song mode. Once you've finished recording, your new wave from Battery 3 will be right there.
"Use the equipment, don't let it use you"