How do you lock the mouse to the viewport?

Hi,
I’m attempting to keep the mouse cursor from moving off the screen using blueprints by setting the input mode to Game & UI and setting the boolean to true. This works but after the first click the mouse is no longer bound to the viewport and can move off-screen.

The game being focused or unfocused to a widget seems irrelevant and re-setting the input mode after a click provides undesired results.

I’ve tried looking at the Strategy example but can’t make sense of the method they use in C++.

Any help from someone whose cracked this would be appreciated.