Changing variable using image source name?

Hey,

Im in the process of building a quiz game with multiple rounds/ levels. I have a screen where you select the round/level that you would like to play. after following the official quiz tutorial I would like to have the round changed to reflect the questions for that round based on the button pressed. I have named the button images in accordance with the round they represent but i need help in having the round data variable change to match the source image name?