Replace MsgBox with WScript.Shell.PopUp

I have an userform that gives the user a message in the string UserMessage.

UserMessage = " added"

I want to replace the MsgBox with the UserMessage to a ("WScript.Shell").PopUp message that should disappear after 1 second.

CreateObject("WScript.Shell").PopUp UserMessage & " added", 1

This code gives me the following output " added" where as I would like to see "UserMessage added".