Stand up straight with a resistance band held in your affected arm.
The other end should be attached to a secure object around floor height.
Turn so that your affected arm is to the side of the secure object.
Place your hand on your buttock with your palm facing outwards.
Gather some tension in the band, and try to pull your arm up your spine.
Ensure you keep your posture upright as you do this.
Only go as far as you can comfortable.
Control the movement as you lower your hand back to your buttocks and repeat.