Payment from variable amount

I’m not sure if we’ve encountered a weakness or loophole in their system. I’ve shuffled and reconstructed quite a few times to their advice and examples however still nothing but errors. I’m thinking to try just doing the calculation then moving to a next page to insert the wixpax coding. That way calculation coding and wipay coding won’t be mixed in together. And the onReady function will operate correctly. I’m still awaiting a reply back again, let me know please if you have any luck