Perhaps the simplest approach would be to use msn or outlook, etc. to PM another user. In order to view who else is in the database you can use the module in the database i linked. Copy paste it into your modules and all you do is hit ctrl+G and type showuser then enter and it will print out a list of other users. I am obviously making assumptions as to why you asked this question, but if I guessed right this should be pretty easy. You could also adapt this to update a form and set the OnTimer to update it as frequently as you wish.
