Hi Nitisha,
I agree with Rajneesh Sir, it is not advisable to change the cost estimate in between the period, that will impact the analysis.
If you want to re-valuate your inventory and match up with the market price per AS-2 standards then consider running cost estimate at end of the period instead of running at the beginning, anyway there won't be major goods movement between last day or previous month and first day of next month. System will revaluate your available FG with the MAP of raw materials as on last date, but it won't re-valuate your WIP and COGS.
If you want to get the actual cost and re-valuate your WIP and inventory with the actual cost then you need to implement Material ledger / Actual costing.
Regards
Bhaskar