Disabling control form fields based on previous input

Hi,

I have a control form, and I am trying to use HTML to disable form fields based on previous input. It works when I try it in preview; however, it stops working when I run the application. Does anyone have any suggestions? For reference, the following video is an example of what I am trying to accomplish: https://www.youtube.com/watch?v=130YJzS2Ekg

If you use a Multi-part form this is relatively easy.
on FormPage1 you can set session vars in the on validate success event … grab the value of the {fieldName} and set them as [sessVars].
Then on FormPage2 you simply check for the [sessVar] and hide/show alter accordingly.