File That Generates Web Galleries In Adobe Lightroom - Use History.go To Find Last Instance Of Index.html Or Index_x.html

I have a file that generates web galleries in Adobe Lightroom. They are generated depending on which files are selected and the metadata in those files.

Basically it is a series of pages of thumbnails called index.html index_1.html index_2.html etc.

Then a set of pages for each individual image.

An example can be seen here: [url](the page navigation links are not great, but I have addressed that, they're at the bottom >> )

Currently if a user clicks on a photo there is a 'return to thumbnails button at the top, but this always takes them to /index.html

So the user could be at a picture after browsing to /index_39.html and still get returned to /index

Is there any way I can use history.go to find the last instance of index.html Or index_x.html (where x is any number) and take them back to that instead?