workItemPublisher ANT task and change sets between two snapshots

Hello RTC Users

I'm trying to compare two snapshots not the current build with the latest build within my build script because this particular build is about an occasional formal delivery. I would like to use the workItemPublisher task, but there seems no mechanism for what seems on the face of it to be a common use case. I'm looking around for some sort of ANT task to produce a changesets file like the TeamAccept does, but between two snapshots of my choice, not just for the latest changes, such that the user can click on the changes URL created by the workItemPublisher on the build result and see all the changesets between an earlier snapshot and this one. Any pointers welcome, or perhaps advice on my approach?

Cheers

Richard