group policy

Hi all
i'd like to block any client of my network to prevent them changing
only the Advanced button under Control Panel- internet option-
Connection-LAN settings
I only want to grey out the button Advanced in the Proxy Sever
settings, but NOT the other check boxes
Have you ever implemented that via Group Policy?
I have searched for every option in gpedit.msc in my Windows server
2003 but i cannot find the related policy
Thank you very much

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