Sounds like you're convinced not to do it, but here's an example. This character stands up and runs off screen. I've added grid lines to the sprite sheet to make it easier to understand. This guy only has 2 images for running, but they're repeated over and over as he moves across the frame. Here the frame is 48 pixels wide. To run across the whole screen the frames would need to be 600 pixels wide, and there'd need to be about 12 times as many as I have here.
CO's are really best for mostly stationary objects, like a TV or a Cow.
[Custom Object 28]
Image=SkullRun.png
Tile Height=24
Tile Width=48
Init AnimTo=19
Init AnimRepeat=1
Init AnimSpeed=400
Offset X=12