Thank you for your response.
my problem is, i already have some members who registered previously in my web site. and now i installed CBSubs to my system.
i imported them to a existing users plan. untill here everything is okay.
for example regarding to the plan, they will expire on the 20th of june.
I want this; after the 20th of june, i do not want them to access their control panel which is
www.mywebsite.com/administrator/index.php (if not paid)
if they try to access, a message has to be inform them that he has to pay to access their control panel.
I hope that is clear for you.
if not please let me know.
Thanks for your help.