NET SEND is an network admin tool - it's NOT a elegant solution, more a simple workaround hack. but if you must (and the network allows for it)

1) create a subscribers table - this will hold the names and network addresses of those interested in receiving notifications (subscribers)
2) create a trigger on the existing messages table that fires on an insert, within the trigger use a cursor to loop through the subscribers table.
3) for each record in subscribers execute a xp_cmdshell 'NET SEND' on the network address field. continue to loop through the subscribers table until all the entries have been notified.

I only use this for debugging.

..it also makes for a nice wind up.