Dial out on specific port of Grandstream 4-port FXO gateway

[cilcomm]

I have added a Grandstream GXW-4104 in trying to use it with a Bogen paging interface that allow zone paging.

How can i assign a specific FXO port to be used on the Grandstream unit for this paging interface? I dont see how to set up the 4 FXO ports to be in 4 different routes in the SIP trunks or routes

any ideas?