I need to add rows to an existing (maybe) datatable in a dataset that combines the IIS6 index search with my own sql table. I keep getting object reference errors. Anybody help me out?

Code:
If ds.Tables("list").Rows.Count > 0 Then
            For Each k As Data.DataRow In ds.Tables("list").Rows
                Dim myDate As String
                If Convert.ToInt32(k.Item("structure")) = 4 Then
                    myDate = "Online - " & k.Item("eTitle").ToString
                Else
                    myDate = k.Item("mDate").ToString & "  - " & k.Item("eTitle").ToString
                End If
                Dim objRow As System.Data.DataRow = ds.Tables("listSearch").NewRow
                objRow("filename") = "Some Class"
                objRow("characterization") = myDate
                objRow("rank") = "1100"
                objRow("path") = "SomePath.apsx?eid=22"
                ds.Tables("listSearch").Rows.Add(objRow)
            Next
        End If