Is it possible to toggle the "edit" option of a widget?

I would like to make it so that when a user clicks on a boolean (like "use
constraints") it will lock or unlock the field in which they would enter the
constraints.

I can imagine redrawing the whole GUI using a function attached to the
boolean, but that's clunky and slow.
I tried changing the .PBSmod variable... but that doesn't redraw the GUI,
even if you use updateGUI("G") or updateGUI("L")

Thanks!

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