Do you want to view O/L, A/L and Grade V results a bit earlier than http://www.doenets.lk lets us. I have tried it when it says, "New Await Results". You can do this using firebug addon on firefox.
www.doenets.lk lets us to check previous result too. These are displayed by the "New Await Results" table. So what you need to do is first select one of those forms and change action url to exam_OL.jsp, exam_AL.jsp or exam_GV.jsp as appropriate. You would also need to change the size/maxLength of the inputput field as well. Otherwise it won't let us to insert our full index number. That's all, fill it with your index number, submit and get your results. You can also do a http POST using your own form as well.
Attention : I am not responsible for the accuracy of results as www.doenets.lk might not have officialy released the results when you use this.