Dear Suresh,
You are doing reverse calculations. If (Price at 10:30AM - price at openinhg) > 20 then, buy calls at S1. and if (price at 10:30 AM - price at opening) <20 then, buy puts at R1.
In net shell if trend is up by 20pts then, buy calls at S1 and if trend is down by 20pts then, buy...