Thanks to all who replied. The answer is it can't be done - because AAX is a locked add-on, not a floating license, the only way to transfer the license is to shut 'em down.
This may be a foolish question, but here goes.
We have 1 seat of AAX, installed on two machines. Currently, whoever launches Pro/E first in the morning gets the seat of AAX. If the other user needs to use AAX throughout the day, the only way we know of to switch the license over to the other user is for both users to shut down Pro/E, and then the user who needs the license re-launches Pro/E first. Is there a way to transfer the license over to the other user without both parties shutting down Pro/E & restarting?
The solution is to define multiple startup configurations when your installing Pro/E.
Make one startup without AAX and the other with AAX.
In the morning when the users start up, they should pick the non-AAX version unless they know they want it that day. Then the person that wants it later in the day, would shut down and re-start except this time pick the AAX license. That way you only disrupt the user that wants to use the feature.
When running ptcsetup, pick Additional License Configurations under the Optional Configuration Steps.
In the licsense configurations window pick Add.
What you enter in the Configuration Description field will be what shows up in the menu. Pick your AAX startup extension and add it to the Selected Licenses. In this example I added the ISDO startup extension.
You can continue creating configurations for as many extensions and floating options you have. In the end the user will be presented with this menu when they startup ProE. Each option is a configuration you created and the name in the menu is the description you gave it.