Posting in the Magento forums has been disabled pending the implementation of a new and improved forum solution which should better serve the community.
For new questions please post at magento.stackexchange.com, the community-run support site for the Magento community. We will be providing updates on the new forum solution soon. For questions or concerns please email firstname.lastname@example.org.
Generally you canÃ¢â¬â¢t do this thing. This requires total customization on your Magento store or site. For this requirement, you will have to develop a module and make coding that provides the functionality to enable or disable the module for theme.