The way you can do this is a "action script" in MXM. You can go to AllXboxSkins.net for the action scripts. Look for 2 called "pw.xas" and "pwscreen.xas". Once you get them, you can go onto you xbox C drive and make a folder called MXMScripts. Then place the 2 files in that 1 folder. Then you can complie a file called MXM_Entry.xml via word. Inside that file make it read something like this(or even copy this and change everything to your settings):::
<Title>Name of the game here</Title>
<Description>dosent have to be here</Description>
<thumbnail>if you want place dir here</thumbnail>
SET DIGIT1a A
SET DIGIT2a B
SET DIGIT3a X
SET DIGIT4a Y
SET DIGIT5a A
SET PWSCRIPTPATH "C:\\MXMScripts"
SET PATHNAME "F:\\games\\name of folder"
SET FILENAME "default.xbe"
Once compilied, place the MXM_Entry.xml inside the root dir of that game! After that, reset menu cashe and now you have it protected!!!!