Adjustable patch setup

Hi, I’m trying to set up a color matching experiment.
I want to have the test surface on the screen and an adjustable patch.
Observers can press button a to make the patch lighter, button b to make the patch darker, and button c to “lock” their match and move to the next display.
Can this be done? Any ideas?
I think this is a very elementary psychophysical procedure and that it would be easy to set up, but so far I’ve had no luck…

Thanks!

In SuperLab 4.5 the feedback can only be based on a correct or incorrect response. However, this can be done in SuperLab 5. In SuperLab 5 you can have a different action for each key press of “a,” “b,” and “c.” The color patch would be done using a Trial Level with the Manual level selection feature.