Repeat region - calculation (ASP)

hi all, i need help from you all

i have a problem as like...

i create db_ewallet (debit,credit,userid)

#########################

#  userid   #  debit  #  credit  #

#-------------#------------#------------#

# John     #   $20    #   $5     #

# John     #   $12   #            #

# Ray      #   $22   #    $12   #

# Lynda   #   $28   #    $3    #

#             #           #            #

#########################

i create table and make repeat region (user id is unique id)

the problem is i cant make a calculation total of debit because John (same people)

the command like this :to calculate debit

<%=(debit.Fields.Item("john").Value) + (debit.Fields.Item("Ray").Value)+ (debit.Fields.Item("lynda").Value)%>

the result appear = $70, the result should be like this : $82