Okay So here goes :).....
Assing an output to be the CLN. Now on the system tab make sure to set your ME 2 Clean Feed position to be before Key 1.
Now you would be setting up your PGM ME to be including all of the keyers when you are cutting between the two and always remember to make sure that the ME1 is under the Key1 when you go back to the boxes...
Key 3 - Box 2
Key 2 - Box 1
Key 1 - Full Screen BKGD....
BKGD - same source as Box 1
PST - Next source you will Cut out too.
Okay -- what would probably be easier though :) would be to put a MiniME downstream of ME 2. Put ME 2 into Key 1 Box 1 and Box 2 with your other source....Then you have your background on BKGD....
In that case you would have an output that is PGM and then another that is MiniME x (lets say 4) which would be what they select for the breaking weather :)
Now you can run your show how you always run the show and not have to work around the fact that you tied up ME2 for the boxes.
#Carbonite