Retriving AP-Invoice Screen values using datasource

Hi...

I am trying to get values from AP-Invoice screen.I am able to get header values using

Dim apform As SAPbouiCOM.Form

apform = Me.SBO_Application.Forms.GetForm(pVal.FormType, pVal.FormTypeCount)

apform.DataSources.DBDataSources.Item("OPCH").GetValue(1,0)

How to get values Of Item Matrix like itemcode,Itemdescription,unitcost ....... Using Datasource before adding to Database tables

please Help...