Remote controlling a BVM from a gscartsw/gcompsw

[gordon-creAtive]

BVM's do have a menu where different settings can be tied to a number from 1 to 8. One of those function is the channel selection. On the back of a BVM is a DSub-Connector labelled "Remote 2". If one of the pins from 1 to 8 is shorted to pin 9, the corresponding setting is applied.
Documentation: http://pdf.crse.com/manuals/3800958081.pdf (See page 17 and page 38)

gscartsw's and gcompsw's on the other hand have an interface labelled "EXT" that enables querying the current input. What I'd like to do is switching my BVM to the corresponding channel depending on what input is active on the gscartsw. Unfortunately there is no documentation on this available yet but maybe superg wants to release some?

Also I'm not an Eletronics Engineer, so I'm not really sure how to achieve this. I guess a microcontroller or even a simple FPGA might be able to pull this of. What are your thoughts on this?