Hello WS7M!
The API for AG can be found here:
gscp.arula.rs/
But I got some great news too. The functionality you're looking for is already implemented into the device.
What you need to do:
1) When configuring your antennas, select the band the antenna is used for but also assign the "none" value to it.
This allows the antenna to be manually selected when no band data is available
2) Assign your FlexRadio band data to one radio port (A for example) and leave the other port without band data.
This way when your going trough bands A side will automatically select the proper antenna for the band while you'll be able to select any "none band" antenna on the B side with your mouse.
Is this what you were looking for?