Add a new voice to Windows right-click menu

Question

I would to add a voice to the right-click inside a textbox of Windows menu. Try to imaginate google inputbox (textbox) where you write the key to serch? Ok, if you right-click above it shows right-click Windows menu (copy-delete-cut...) I would to add a new voice, i know i can do it by Registry key, but how? Please answer me, thanks.