Sending Messages to Users as Screen Pop-up

Can anybody help me how I can customize a form/menu to send users messages as Screen pop-up?

Also, how does the "Send Message" Command work in Admin module?

Please share any form/methods/macros if available.

Thanks in advance!

I am trying to send the message to users by using "send Message" window from utility option provided in ADMIN module.
But it is not working. I request to experts to help in this regards.
Thank you.
Mahesh Netke.

This is a quite old utility used when emails were not existing yet...
If I am not wrong, interested users would read their messages on the console window at next module switch.