Net Send Messages Via Mikrotik Os

How Can i send messages all over the LAN ( Like Net Send Command) Via Mikrotik OS?

You cannot.

is’nt “net send” a part of the Microsoft Netbios thing?

Yes, it is.

So is there any option in proxy server that users can see Welcome page first before connect to net ( Like WebTOS In ISA 2004)?

Hotspot with hard coded user credentials