Hello K C Das

You cannot use a visual Basic Message Box this is deactivated in WinCC Comfort/Advanced.  if you use a Panel Version V13 or newer then you can use a Popupscreen. You cannot call the popupscreen in the Faceplate internal, co you have to set the event as an interface to the "outside" then you can show the popupscreen.

The result you have to write to an interface tag too to get it back to the faceplate instance-

Bye Murof