573000 Update OsCommerce 2.3.1 php menu

I have an OsCommerce website that has a database driven Categories menu on it that I need modifying. This uses a file called [login to view URL] to create the menu. If you have a look at [login to view URL] and there is a Categories menu on the left. If you click on Wines-> it expands the menu to show all the countries that produce wine. The problem is that at this point it is also opening a page showing all the countries as images with text underneath them. We want the menu to just expand when you click on the top category if it has sub-categories and to leave the current page in place, but when you then click on a country (sub-category menu item) to then proceed and open a new page and expand the menu. To summarise: If a top level menu item has sub-categories – just expand the menu, do not open a new page. If the top level menu has no sub-categories – display the items in the page. I have attached the file that creates the menus if you need to look at it. If the menu item is a sub-category with sub-categories of its own – open new page and expand menu. Any questions contact me.