Reply To: Optionable to pay percentage Not Working

Unfortunately it is not possible with Authorize as with the other payment gateways.
Their security works by generating a hash of the form itself and add it to the form before displaying. They are doing the same with the form after submit and compare both hashes to ensure the form wasn’t manipulated.
As you change the form by changing the price this check gives false.
To make it work the hash would need get regenerated after changing the price which would need an ajax request, a regeneration script and the javascript part to insert the new hash. That’s like 200 lines of code and a few hours work.
As authorize is really not used much (there were a breaking bug in it and nobody reported it for seven months) I can’t work so much on it and let it blew up my code with 200 unwanted lines.