How to restrict posting for users

Scenario: For the month of March'2012 only one user can post entry and they should be able to post in                  the current open period month. But other user cannot post any entry in the system...is it                          possible? If yes how can I restrict. Is it possible from functional end or it is possible from                        technical end?

Solution: This can be solved by modifying the way you use the OB52 screen, 

To solve the above situation, we maintain is this way.. From Per1 -- To period ( which controls Mar' 2012) , From Per2 -- To Period is open for AUGR  0001

and From Per2 -- To Period is open for all.