not sure what you mean but do you want the phone to stop using adw and start using launcher pro? or do you want your layout from adw to go to launcher pro? you cant do the second one... i can tell you the first ?'s answer if thats it...
I set the default home screen as ADW but I want to switch it to launcherpro, but since I already set ADW as default it won't give me the option to choose from ADW and launcherpro anymore when I press the home button