Quote Originally Posted by speedminded
Doesn't matter if the conveyor belt is still or moving forward or backwards at 5 mph or 500 mph.

Imagine a skate board on a treadmill, you can prevent it from moving backwards with just a finger right? Speed up the treadmill and it wouldn't take any more effort of that one finger to hold it in place right? No matter how fast that threadmill is moving couldn't you still push the skateboard of the front of the treadmill?
If you pushed the skateboard forward, the treadmill would not be moving at the same speed. If you pushed it forward, the skateboard would be moving faster than the treadmill in the opposite direction. That goes against what the OP said, therefore it can't happen.