Montly budget control in BCS

Hi Gurus

My requriment is about budget which can be possible entry month base. For example, i only  want to entry budget for february. I defined 2 document types. one of these is budget ( B1 ) and the other is release ( R1 ). I entry budget for period 2 in FMBBC selecting budget. After that i went to FMMPRELE. I released 100 percent of budget for period 12 when i check total table FMAVCT i see budget only period 2. But when i post a document which has document date january in f-02 the AVC is working for january also. I want to the sytem control only february. Is it possible?? IS it possible  If i use  EXIT_SAPLFMFC_002 ???

Thank you very much