After an exhaustive search, I’ve determined that the AJAX request, javascript code that runs asynchronously in the background isn’t something I can get a signal from in any way. It does seem to trigger some event when it finishes with loading the page, which is an option I’d like to explore in the future. However, for my purposes I simply used the same code I was already using to fill out the form on my page and I have it loop through each field again to check to see if the values are still correct before clicking the submit button. It isn’t an ideal solution, but it is a workaround that appears to have taken care of my issue in this case.
I’m not sure if my solution would be applicable to someone else dealing with this issue, but there it is if it helps. I think workarounds for this issue are going to have to be based on the application and web page in question.