At which Enhancement point I must write code doing authority check for MRRL "Test Run" ?

Hello Gurus,

Please guide me here. In MRRL t-code I need to make some changes wherein Test Run checkbox must not be allowed to be unchecked by a set of users (I will always remain checked for them). I created authority object , a role and assigned those users to this role. Now, I want to know at which Enhancement point should I call this authority object and handle the checking/unchecking of checkbox based on authorization.

Thanks and Regards,

Chetna D