INT 21 - LANtastic v3+ - POP UP LAST RECEIVED MESSAGE
AX = 5F9Ch
CX = time to leave on screen in clock ticks
DH = 0-based screen line on which to place message
Return: CF clear if successful
CF set on error
AX = error code (0Bh)
Notes:  the original screen contents are restored when the message is removed
the message will not appear, and an error will be returned, if the
screen is in a graphics mode

See also: 215F9A

215F9C - LANtastic v3+ - POP UP LAST RECEIVED MESSAGE