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

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