How can I prevent the user from going past the Results Screen?

Remove the OK button at the bottom of the screen when the final results are displayed. This is done when designing the Results screen by adding the command "LastScreen". This can be any line in the screen commands. To add it, go to the Screen Command Builder and pull down the dropdown next to "Buttons" and select "Last Screen".

If you were using the default Results Screen which has no commands, build a screen with the two commands "VARIABLES" and "BUTTONS: LastScreen". This will behave like the default screen, but will remove the OK button.