Hi Ramakrishna,
You can use period wise budget control tool ,if you don't want to carry forward monthly residual budget to next period. If you want to carry forward,you may create one Budget entry as transfer posting between one period to another period by FMBBC or else standard BAPI ,if there is large data.
Above scenario is standard scenario.
Other wise,you can use above mentioned user exit and call table FMAVCT table where you can get the planed values with actual s ,where you have to put logic ,if period 1 budget not exceeded with plan against actual.
Regards
Mani