Categories in Outlook

Hi all,
I can’t figure this out. Outlook has categories, which can be assigned to each email message (similar to gmail’s labels) and are stored as properties of the message. I would like to select all the messages in a particular inbox with a particular category. This below throws an “invalid key form error”, other versions of this snippet don’t work either. Any suggestions? Much appreciated.

All the best
G

tell application “Microsoft Outlook”
set mailAccount to first exchange account
set myMailbox to folder “Archive” of mailAccount
set myMsg to messages of myMailbox

my ideal command would look like:

#set mySubset to (every message of myMailbox whose category id contains 25)
#but that doesn’t work. I can’t get to work even the simple command below:

if category id of myMsg contains 25 then
	log "found one"
end if

end tell