Combine sources for target tag

Hi there,
Sorry if the title doesn't make sense.
What I want to try and do is combine the PUBLISHER tag from Discogs with the CATALOGID tag from Discogs, so that it ends up being:
PUBLISHER - CATALOGID
So a really working example would be:
Rocksteady Disco ‎– RSD015

The first part being the record label and the second part being the release. And I would like all is to go into the Grouping section on Itunes/Mp3tag.

This means I can search for a record label in Itunes, plus I also get the release information.

Is this possible? Or does anyone have a better way?

To copy the contents of 2 fields into one, use an action of the type "Format value" for the target field
Format string: %PUBLISHER% - %CATALOGID%