ssrs reports

i am making a SSRS report using dp class on customer transaction but the problem is i wanna show balance separately in debit credit column. i hv used display methods to do this but i didnt get the result.....so plz help me

i m giving u the code which i hv written 

[
    SysOperationLabelAttribute(literalStr("@SYS60289"))
]
Display Credit credit()
{
    CustTrans CustTrans;
    AmountMST AmountMST;

    select AmountMST from CustTrans where CustTrans.AmountMST>0;
    return this.AmountMST;
}