Madhu,
As mentioned by expert Caetano, I don't believe that SAP supports your requirement in standard. In general, it is considered to be a 'feature' that dates in the past can be entered.
The most common way to solve this problem is through user training. Management merely instructs the users not to do this. There is enough data available in the system to determine the users who are unable or unwilling to comply; and from this info, management could exercise appropriate techniques to eliminate the behavior.
If user training/management correction is not possible, one method to meet the requirement would be to create a transaction variant that would require the users to enter the required dates. You could then remove the standard transactions from the user's profile, and restrict them to the transaction variants. Your developers and your authorization group should be able to perform these tasks.
If this method was inadequate, then you would probably have to resort to an enhancement. Your developers should be able to create whatever functionality you need.
Best Regards & Good Luck,
DB49