Problem running code

[Aigini]

I created the code below to import an Excel file into an existing M'soft Access database. The attributes present in the Access database are CWNO(Text), Name(Text), ICNO(Text), Nasion(Text), Company(Text), JoinDT(DateTime), ExpDT(DateTime), ResBT(Boolean), ResDT(DateTime), Note(Text), PBIT(boolean). The final four columns are not present in the Excel sheet. (ResBT, ResDT, Note, PBIT).But I seem to have problems with the code, but do not know why. I've been trying to find out what's wrong since yesterday, but I do not know why. Please help. The error message that I get is "Conversion from type 'DBNull' to type 'String' is not valid". How do I correct this error?

Private Sub loadDataFromExcel()
        Dim excelFile As String = "C:\Documents and Settings\SL\Desktop\Project\CW 2008I-Update.xls" 'replace with valid path - file
        Dim ExcelSheet As String = "[Sheet4$]"
        Dim sqlExcelData = "SELECT * FROM" & ExcelSheet
        Dim TableToImportTo As String = "CwMaster"
        Dim NumberOfRows As Integer 'CurrentRowPosition As Integer
        
        NumberOfRows = cwmasterTableAdapter.GetData.Rows.Count

 Try

            Using ExcelConnection As New OleDb.OleDbConnection
                ExcelConnection.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _
                "Data Source=" & excelFile & ";" & _
                "Extended Properties=""Excel 8.0;HDR=NO"""

                Dim da As OleDb.OleDbDataAdapter = New OleDb.OleDbDataAdapter(sqlExcelData, ExcelConnection)
                Dim I As Int32
                Dim K As DateTime
                ExcelConnection.Open()
                da.Fill(cwdbDataSet, TableToImportTo)
                For Each Row As DataRow In cwdbDataSet.Tables(TableToImportTo).Rows
                    Dim masterCwRow As CwDbDataSet.CwMasterRow = cwdbDataSet.CwMaster.NewCwMasterRow()
                    With masterCwRow
                        ' Some columns may require changing the Datatype
                        ' Excel columns that contain numbers and blanks are considered STRINGS   so they
                        ' Need to be converted

                        

                        If Not IsDBNull(Row(0)) Then
                            If Int32.TryParse(Row(0), I) Then
                                .CWNO = I
                            Else
                                .CWNO = 0
                            End If
                            .CWNO = Row(0)
                        End If
                        .NAME = Row("Name")
                              
                        .NASION = Row("Nasion")
                        .COMPANY = Row("Company")
                        
                        If Not IsDBNull(Row(2)) Then
                            If Int32.TryParse(Row(2), I) Then
                                .ICNO = I
                            Else
                                .ICNO = 0
                            End If
                            .ICNO = Row(2)
                        End If

                        If Not IsDBNull(Row(5)) Then
                            If DateTime.TryParse(Row(5), K) Then
                                .JOINDT = K
                            Else
                                .JOINDT = Nothing
                            End If
                            .JOINDT = Row(5)
                        End If

                        If Not IsDBNull(Row(6)) Then
                            If DateTime.TryParse(Row(6), K) Then
                                .EXPDT = K
                            Else
                                .EXPDT = Nothing
                            End If
                            .EXPDT = Row(6)
                        End If

                    End With
                    'Add the next row
                    cwdbDataSet.CwMaster.AddCwMasterRow(masterCwRow)
                Next
                'Apply changes to the physical database
                cwmasterTableAdapter.Update(cwdbDataSet.CwMaster)
                cwdbDataSet.AcceptChanges()
                'Close connection and clear the dataset to avoid duplicate rows in table adapter
                cwdbDataSet.Tables(TableToImportTo).Rows.Clear()
                ExcelConnection.Close()
                ExcelConnection.Dispose()
            End Using
        Catch ex As Exception
            MessageBox.Show(ex.Message)
        End Try

   End Sub