Open the ABP_BaseHoldableAnimLayer then open the UpdateHand IK Data function and copy the image below. You will need to create 2 new local variables, set their type to Float and name one DisableLeftHandIKL and DisableRightHandIKL

Make sure you set the Curve Name values on the Get Curve Value nodes correctly and make sure on the Nearly Equal (Float) nodes you set the B values like shown in the image.