According to Comparison of file archivers - Wikipedia, the free encyclopedia
7-zip supposedly supports multi-volume archiving.
However, according to SourceForge.net: 7-Zip: Topic: command line and updating a volume set
, Igor says that once you've made the multi-volume archive you cannot update it.
All the research I have seen as well seems to point to commandline only use, however it is odd that the Wiki does not make note of this at all.
You do have another option - IZArc Free Zip File Archiver | Free Software Full Version
And WinRAR does both
.ZIP formats, and it integrates into your system very well (and even 64bit OSs now too).
The best part is that the license I bought in 2002 is still good today - a one time payment (then only $20) has lasted me this long, and it is the main reason I keep it around.
However, it's performance is getting out of date - other archivers get better performance *and* better cost less, so...
The choice is yours.