how to use datepart

Question

hi,
   i have two table one is EmployeeImprestPaid and second is EmployeeImprestReceived.On page ImprestAccount i have three gridview
one showing ImprestPaid,second is ImprestReceived and the third one is
Outstanding.

 showing like...
                  ImprestPaid
  
      Paiddate                       Amount
       06/21/2009                    1000
       06/23/2009                     500

ImprestReceived

Receiveddate                  Amount
      06/24/2009                  1000
      06/25/2009                    300
outstanding

month     Amount     carry forward
  June          200               200

suppose in PaidImprest grid entry in enter with date 07/20/2009
ImprestPaid
  
      Paiddate                       Amount
       06/21/2009                    1000
       06/23/2009                     500
       07/20/2009                     1000
then outstanding will be like
month      Amount      Carryforward
 June            200              200
 July              1000            1000
please help me...Thanx...