Dynamically add an Infusionsoft tag?

Hi, I need to be able to add an Infusionsoft tag (or tag ID) to the GET data that is passed to the form, and have the form take that data and tag that contact appropriately. I see that there is a tab where I can add specific tags to the form that are always added, but this isn’t what I want to do. I need to be able to add a different tag to the contact based on what they selected on the previous page. I see that it is possible to add hidden form fields that add GET data but it appears there is no protocol in Infusionsoft for doing this. Is there any way I can pass a tag ID in using GET and have the form add the tag to the contact? Thanks so much!