when (I hit send)
  if (the "source" account is "myuserid@gmail.com")  then
    if (there are addresses in TO or CC that match "work.com")  then
      pop up a dialog box that says:
         "You appear to be sending email to work.com from gmail.com - do you really want to do this?"
            if yes, then send it and return
            if no, go back to the message compose window