retreive price from matrix before sales order added

hey All.

I have the following code to retreive the PriceAFVat col from a matrix before a sales order is added into the system:

See simplify version of code below.

oDBDataSource = oSapSalesOrderForm.DataSources.DBDataSources.Item("RDR1");
f
or (int i = 1; i <= counter - 1; i++)
{
        docLineMtx.GetLineData(i);
        locTaxDetail.GrossAmount = Convert.ToDecimal(oDBDataSource.GetValue("PriceAFVat", oDBDataSource.Offset));
}

can anyone tell me why that field and many others are empty strings when the form is in add mode? Fields such as itemcode are available. How do i get the price for the matrix line if this is the case?