Using midi in logic to control NI Guitar Rig

HI

I want to play my guitar using NI Guitar Rig on my MBP against a backing track, also on my MBP. I want to automate patch changes in Guitar Rig as I play so I dont have to use any MIDI floor pedals to change patches in GR, that is I want be able to change the patches in Guitar Rig from (say) clean to crunch via dialling in the midi patch changes in a track in Logic at the significant times along the track. I used to be able to do this easily in Cubase and Vision before that, but cannot think how it works in Logic. Can anyone help?

thanks