How to read system matrix

Sir,

A/P Invoice has 2 document type i.e Item/Service with a matrix item(38)

I am able to read all the columns of DocType Item using VB Code for data validation

" oEdit = oColumnsTemp.Item("112").Cells.Item(pVal.Row).Specific

temp = oEdit.Value "

But i am not able to real any of the columns of DocType Service using VB Code for data validation

I need ur kind help/support

Thanks & Regards

Rajesh B K