Have you tried under Functions->Time & Dialog->One Button Dialog? This is a wonderful way of pausing until a user presses a button.
If you wanted, you could use a textbox and just wire a string to it. Then clear it (or hide it using a property node) when done.
If you want to use a boolean indicator, there is a property (in the property node) called "Strings". This is a 1D array of strings for False, True, Transition True->False and Transition False->True. You can programmatically change the strings.