open price discovery

How can I place a buy order such that I buy it at stock opening price of the day?

From 18th Octiber, normal trading hours has been moved from 9am to 9:15am. First 15 minutes, i.e, 9am to 9:15am will be used for open price discovery. This will be called Pre-open session. The NSE weblink contains the details about the open price session...