How to extend the (Page)restriction dialog / user-group search

Hi there,

could anyone push me in the wright direction? I’m searching for a way to extend the (page) restriction-dialog in that way that I’m able to control the user/group search. If you resrtict the page and search for a user I want to add some extra information about the user eg. additional information about the LDAP-pool the user has been found in…

I also want to control the groups that are returned - in that way that I can add some filtering and do not return all the available groups for some (logged in) users…

Any hints?
Thank you very much!