Hey, @Joe_Gillespie,
So to do that you’re best off using a “middleware” approach. Basically, when they ‘submit’ information through the url, you send it to a middleware script. Doing this allows you to use the script to update Infusionsoft first and then the script can redirect to the thank you page. It’s pretty quick and virtually transparent to anyone that’s not familiar with programming and is a common way to solve for what you are doing 