Test to see if message box was closed with "X" Button VBS

Hello (Two questions in one night may be overkill but I'm down to the last minute!) I am trying to launch files based off of a user choice from a message dialog with vbs. This works however I want to test to see if the user clicks the "X" button in the top right corner instead of clicking "OK" Here is the code I have.

set shell=createobject("wscript.shell")
x=msgbox("Message...." ,0+16, "Error:")
If x=1 Then
shell.run "P:\Test.bat"
End If

However I want to use an if statement to test if the user clicked "X".