Yes, ProgDVB does require a plugin to operate a Diseqc motor.
There are a few out there, but the one I use is called Dixie.
Jyst add the plugin to the root directory of ProgDVB and then set it up within progDVB.
of course you motor should have been setup correctly in the first place and the positions already stored should match the dixie.ini file supplied with Dixie.
Cheers.