Here is the jist ezkimo,
<control type="button" id="17">
<description>Play Disc normal push button</description>
<posx>375</posx>
<posy>414</posy>
<width>305</width>
<height>40</height>
<!-- <include>10009</include> -->
<label>Movie Trailers</label>
<onclick>XBMC.RunScript(Q:\scripts\Apple Movie Trailers_v0.96\default.py)</onclick>
<onleft>18</onleft>
<onright>10</onright>
<onup>31</onup>
<ondown>5</ondown>
<texturefocus>default-button.png</texturefocus>
<texturenofocus>-</texturenofocus>
<textoffsetx>22</textoffsetx>
<aligny>center</aligny>
</control>
<control type="button" id="37">
<description>Play Disc hidden push button</description>
<posx>375</posx>
<posy>414</posy>
<width>305</width>
<height>40</height>
<!-- <include>10009</include> -->
<label>Movie Trailers</label>
<onclick>XBMC.RunScript(Q:\scripts\Apple Movie Trailers_v0.96\default.py)</onclick>
<onleft>18</onleft>
<onright>10</onright>
<onup>31</onup>
<ondown>5</ondown>
<texturefocus>default-button.png</texturefocus>
<texturenofocus>-</texturenofocus>
<textoffsetx>22</textoffsetx>
<aligny>center</aligny>
</control>
<control type="image">
<description>Disc Focus arrow image</description>
<posx>640</posx>
<posy>396</posy>
<width>25</width>
<height>75</height>
<texture>home-buttonarrow.png</texture>
<aspectratio>keep</aspectratio>
<visible>[Control.HasFocus(17) | Control.HasFocus(37)]</visible>
</control>
<control type="image">
<description>Disc arrow image</description>
<posx>640</posx>
<posy>396</posy>
<width>25</width>
<height>75</height>
<texture>home-buttonarrow-alpha.png</texture>
<aspectratio>keep</aspectratio>
<visible>System.HasMediaDVD</visible>
</control>
That is the TYPE of change you need to make, the above will give you a button right below System in the xTV skin, it will also look really bad if you have a disc in, and the animation will be off, but above is how you would need to do it, I tested it, and it works fine.
You press down from System, the Apple Movie Trailers gets highlighted, when you press select, Apple trailers opens right up.
Use the above as a idea, and make it look the way you want it.
Hope it helped.