How to add a item in WPS context menu?

[yzflcyq]

Hi everyone,
    I'd like to add a item in WPS context menu which when I press it, it starts /.rockbox/apps/snclrc.rock.
I think it works like the PictureFlow item. But I tried to add and compile, the compiler told me GO_TO_LYRICS undeclared.
    I want to know what files should I edit and how to edit these files. I tried to read the PictureFlow item code and onplay.c, onplay.h but I can't understand them.
    Thanks you.