To disable the CD-RoM and enable

i have CD-RoM in working order on my pc.i want to disable my CD-Rom for a limited time,no body access it,without physicaly disable from pc.when i want to use it, i use it. i know a little bit that it could be done by giving a command on DoS-propmt,but i forget that command.it is just like password
to protect your CD-rom form others.please help me.