How can I move a block when it is placed without the piston interfering

I'm trying to make a redstone device with the new concrete powder where the blocks are being pushed along a row, but every time a block reaches the end, the whole row is pushed up. However, I've tried block update detectors and it doesn't work to power the piston underneath. Because the piston pushes up to where the block reached the block update detector, it powers the piston again, creating an infinite loop. Is there any way to avoid this? I want to avoid making timers, so is there a way to make some sort of pseudo-block update detector that isn't triggered by the piston, or some other device that does the same thing?

I think I understand what you are trying to make here, and I have came up with this, All you need to do is to make sure that the side piston is set on 4 ticks, and run the observer output into that, this will slow down the piston movement, giving time for the block to be pushed and not creating an infinite piston moving loop.