Hi Sandeep,
In addition to what Caetano and Debashis has suggested, I hope there can be a work-around via MRP so that you may get start and finish date according to the MM MRP2 view in-house production time.
Please try to test the following scenario:
1. In Production Order scheduling setting OPU3, maintain Adjust Scheduling as "3 Do not adjust basic dates, dep. reqmts to order start."
2. Create some requirements for the produced material.
3. Run MRP using basic scheduling; i.e Scheduling = 1.
4. Now try to convert those MRP generated planned orders using CO41.
Best Regards.
Rajen