property yourproject : "Put name of your project here"
 
tell application "Microsoft Entourage"
    
    -- get the currently selected message or messages
    set selectedMessages to current messages
    
    -- if there are no messages selected, warn the user and then quit
    if selectedMessages is {} then
       display dialog "Please select a message first and then run this script." with icon 1
       return
    end if
    
    repeat with theMessage in selectedMessages
       -- get the project list from the message, add "YourProject" to it
       set theProject to project list of theMessage
       if {project yourproject} is not in theProject then
          copy project yourproject to end of theProject
          set project list of theMessage to theProject
       end if
       set storage of theMessage to folder yourproject of folder "Projects"
    end repeat
 end tell