New Shoulder Workout

Hey guys,

I was watching Jamo's shoulders and back superset video where he mentioned that it's always good to be creative and come up with different exercises to hit a muscle group at different angles (man that was a long sentence!).
So i thought about this exercise . I don't know whether there is such an exercise out there so i wouldn't say that i "came up" with this exercise .

This is how it goes. I'll try my best to explain.

Basically, its an exercise of 3 sets X 12 reps performed with dumbells.

The motion is:
1. Do a front lateral raise
2. MAINTAIN ur arms at the top position (parallel to the ground)
3. Move ur arms outwards to reach a side lateral raise position (arms still parallel to the ground)
4. Bring ur arms down

That's for rep 1. For rep 2, u reverse the motion (instead of starting with a front raise and moving to a side, u start with a side raise).

So basically, u alternate this 2 motions (so there will be 6 reps of each).

My question is:
Is this workout effective or does it cause any form of injury?

Thanks ! :)