[Freeswitch-users] FS -route to next GW if the first GW full

i have two media GWs connected with FS for PSTN calls, FS route the first one in normal case, once the first GW get full (all of channels were occupied), i need FS route to the second GW. i found once the first GW get full, it will reply '404 not found' to FS, can FS route to the second one according to this condition or any other alternative? although i know there is mod_distributor for load balancing, however, i need if only first one full then route to second one, so it looks this module not suitable for this senario... Thanks. Regards, Charles