you will need a categories and subcategories table:
categories:
categoryID - Primary Key
categoryName
subcategories:
subcategoryID - primary Key
subcategoryCategoryID - relates to the categories.categoryID column
subcategoryName
the links from the category listing should pass the categoryID as a url variable
the recordset that shows the subcategories should use the URL Variable to filter the subcategory table using the subcategoryCategoryID column