Hi, I'm not much with cows but I think you could apply a similar solution with my own. I raise goats. I use PVC pipe and 2x4's. I make a divider in the stall, and inbetween the bottom and top parts, which have circles drilled into them where the pipes will be place, the pipes line up horizontally to keep the bigger animals out. With either wholes through the wood or just impressions the pipes and "spin" or rotate so that the animals can slide in and out.
Hope I helped with your idea, sorry I wasn't much help :/
I've got factory made creep feeders, so I can't help you much, but I would caution you about not using pvc pipe. Cattle are a whole lot stronger than goats, and will quickly wreck anything that is not built extremely strong. Whatever you do, make it twice as durable as you think you will need. And---good luck!