Help with grippers and collision sensor

Hi everyone,
so i'm moving my first steps in robotstudio and i would appreciate your help.
So i'm using a smart gripper servo with the YuMi 14050 and this is what i'm trying to achive:
when the gripper finger are closing and detect an object stop the movement (and eventually open the finger completely).
I tried using one PoserMover_Close (that close the fingers) and linked it to a collision sensor than, once executed, is linked to another PoserMover_Open that should open the fingers gripper.
Of course this doesn't work because the fingers close completely even after the collision sensor is activated.
Can't figure out how to stop this movement.
Can anyone help me?
thank you so much.