Entering "volume" in references to multi-volume works

Hi,

I frequently cite classical texts that are published in several volumes. I use EndNote X9, and as it is now, I have to create one reference for each of the volumes of the work (it can sometimes be up to 20 volumes). Of course I would like to have only one reference for each multi-volume work. The only way to keep only one reference, and enter the volume in the citation, is to enter the volume in the pages field in the editing dialog box. I would greatly appreciate if you made it possible to enter the volume in a specific field in the editing dialog box, just as it is now possible to enter pages.

/Torsten