This action runs when a user membership request for a group is denied.

 do_action('pm_user_membership_request_denied',$gid,$uid);

Simple example

function profile_magic_action_on_request_denied($gid,$uid)

{

//do something with the user id and group id when a user membership request is denied.

}

add_action( 'pm_user_membership_request_denied', 'profile_magic_action_on_request_denied');