Category Button link to external file

[ukbob]

I am attempting to run a price comparison engine outside of wordpress - but intend that it should appear as an integral part of my Rev City Site. I have the separate engine running ok and it sits within the same domain in a subfolder. Effectively, I have re-created the whole of my Rev City appearance so that it appears seamless. My problem is the external link within wordpress. I guess what I need is an external button on the nav bar. Currently, I have created a category - and then altered the relevant category-ID.php file to point to this subfolder. But its not working.

It worked ok when I used an include on the category-ID.php file (and retained the Wordpress Rev City header/footer) during testing. But now that I effectively want to link to and launch this 'duplicate' site using the same procedure - I get a "file/directory doesn't exist error" . The internal oath is absolutely ok - I can launch a test html file in the same directory ok.

As the include approach was obviously no longer correct - I tried using the 'require' function instead. Same problem.

So, I guess I have to create a traditional button link on the nav bar? Not sure how to achieve that within Wordpress - or is there another way to get this category button to point to my engine folder's index file and load it?

Hope somebody has a great idea!