Version upgrade & product upgrade licensing

Hi there

We are running version 6 at the moment and have been advised that our license allows us to upgrade to version 7 at no charge. However I am also considering switching from Professional to Enterprise versions.

We are almost exactly halfway through our Pro versionannual license subscription, so my question is; if we wanted to upgrade to Enterprise v7 would we be able to pro-rata the cost of the upgrade so that our licensing date is maintained? (That will help me get the purchase agreed this year.) Failing that, can we offset the remaining value of the Professional license against the purchase on an annual Enterprise license?

Thanks
Liam @ SDG