Correction deed

Hi, We registered agreement to sale in order to purchase a flat from my brother in law and my sister who were both coowners in the same property. I applied for the bank loan. They told me that they wont be able to disburse the loan amount until sale deed is registered. My brother in law lives in bangalore so its difficult for him to find time to travel and come to pune to do the registration. Finally we planned sale deed in last week but during that week bank was unable to process the loan in time as they were having some technical difficulties a day prior to the registration. But we went ahead with the sale deed and i provided my check as mentioned in the schedule. Now in order to get the loan disbursed from another bank i will have to do the correction deed. So i'm thinking of registering POA for the flat in Mumbai as my sister stays in mumbai and her husband comes there after every 15 days. Please suggest how to do it and what are the charges for the same. I really need to get the loan amount disbursed.