Are you limited by the order presented in the routing rules?
For example for a recent United fare
ROUTING 550 FROM LAX-UA-LAS-
VIA UA-DEN-UA-DTT/PIT-UA-CHI-UA-
NYC/EWR/PHL/CLT-UA-WAS/ORL/TPA-UA-MIA-
TO UA-RIO*
OR TO UA-SAO-YY-RIO*
becomes
LAX-UA-LAS-UA-DEN-UA-DTT/PIT-UA-CHI-UA-
NYC/EWR/PHL/CLT-UA-WAS/ORL/TPA-UA-MIA-UA-RIO*
Do I have to do WAS before MIA?