Hi Mhaus,
In your file it looks like the pink bar is resizing as the left handle drags, but is resizing from the wrong anchor point; rather than having the left handle’s Set Size action use “anchor top left”, have it use “anchor top right” so that the right edge of the pink bar stays stuck to the right handle, while the left edge adjusts as the left handle gets dragged. For the right handle you’ll want to do the opposite and have the Set Size action for the pink bar anchor to top left.
As far as why the right handle wasn’t resizing the pink bar, it looks like the Set Size action on the right handle had a formula set up, but there were no local variables defined to tell the prototype what subtracting “[[rightpointer.left - leftpointer.right]]” was supposed to do. If you add your local variables that define the pointers as the right and left pointer panels, then this should fix that interaction:
To fix the little gap that seems to appear between the handles and the edge of the pink bar, you can add half of the handle’s width to your Set Size formula, inside of the brackets (e.g. “[[rightpointer.left - leftpointer.right+17.5]]” to fill in that space.
Hope that helps!
Hopefully that helps!