Add item to Links palette flyout

Hi all,

I'm trying to add a custom item to the flyout menu in the Links palette. Basically it would behave exactly like this http://in-tools.com/article/scripts-blog/convert-colors-to-grayscal-in -indesign/, but instead of putting it in the Color palette, I need to use the Links palette. Obviously the item/function I'm adding would be different too. I've been trying every combination of menu name, palette name, submenu name, etc., but I can't seem to find the correct one to allow me to insert my own item. For the menu, I'm referencing

$ID/LinksPanelPopup

which appears to be correct. It's just the flyout menu that I'm having trouble getting into. Anyone have any idea on how to properly add an item right below the "Relink File Extension..." option? Thanks!

Nate