Behavior Biting coroplast instead of wheeking

Elvis gets veggies twice per day -- "breakfast" at around 6am and again in the late afternoon ("dinner"). He always has access to hay. When Elvis wants dinner, he used to just start wheeking like crazy -- but lately he's stopped wheeking almost entirely and instead will just start frantically biting the coroplast and metal bars of his cage. He will start this behavior anytime after 3pm and once he makes up his mind, he will not stop til he gets what he wants. He pretty much never does this before 3pm. He will only do it if he sees me or hears me rattling bags (he associates those with the veggies) in the kitchen in the late afternoon. Sometimes he doesn't bite at all and I'll just feed him when I feel like it (I prefer to feed him closer to 5pm just because I am more consistently home at that time, but I will feed him earlier if we need to go out or whatever -- but never before 3pm). Anyway, he has totally torn up the top of the coroplast in the portion of the cage that is closest to my kitchen. I am worried he's going to harm his mouth or teeth. Does anyone else's pig do this? Is there any way I can discourage it? We say "No Elvis!" very loudly and I've even put my hand in to shoo him away from that spot but he just goes right back over to it as soon as I take my hand out. He will only do this when he decides he MUST be fed. So it happens frequently at that 3pm time and sometimes again in the evening when my husband comes home (my husband usually gives him a piece of tomato in the evening, so Elvis expects that). I imagine he also does it in the morning but basically my son comes downstairs, goes straight to the fridge, gets his plate (which I prep the night before) and gives it to him right away so he doesn't have to wait very long for his food. His cage is right in the center of our house so he can see into the kitchen, den and living room from where he's sitting. Thoughts?