Rescheduling American visa lottery interview date is allowed in some countries and it is too under conditions while in many countries it is totally not accepted. So if you want to re-schedule your DV Interview read your local US Embassy instructions on it. Most of them require medical certificate from the DV Lottery winner.
So here it is. You will receive the second letter - Interview date from the KCC 4 - 6 weeks before the scheduled interview date. That day you will pay the non refundable visa processing fees and you will face the interview. There they will check your personal, education, medical, police report, affidavit of support and other documents. If everything is perfect, they will issue the visas. Otherwise they will ask you to provide the missing documents in time and it should be done before 30th September.
Some people say they are not ready with the documents and want to postpone the interview date.
To this you must contact the consular officer in their country through their official web site and do as required.
But for Bangladesh born people it is clearly stated that they will lose their chance if they didn't appear for the interview on that particular day.
Also if you are going to rescheduling your interview date take note of the following facts,