Associate with sub node with a menu item (but linked from menu)?

Am stuck on this one. Basically I have a menu item called "Menu 1" which links to article "Article 1". When I click the menu to the article, it loads and the menu item changes colour to show where in the navigation I am, which is good :)

If in "Article 1" I say 'for more information go to this page' it then loads a new node "Article 1.5" and whilst relevant to "Article One" wasn't actually linked from the menu and so the menu doesn't change colour, which is bad :(

How do I associate Article 1.5 with the menu item so that Menu 1 stays selected?