Nah your doing it the hardest way possible lol. If your monitor has a HDMI output, connect HDMI from it to your Xbox (but heres the clever bit) Microsoft doesnt want you to do this so they made the original AV input bulky so you cant connect both HDMI (for video) and AV cords for sound at the same time. You need to go at it with a screwdriver and snap the casing off. Thats what alot of people (including myself) do.
Good luck