ممكن المساعدة في كود الإضافة

السلام عليكم ور حمة الله وبركاته

مشكلة كودي أنه الى قبل ساعة كان يضيف في الداتابيس والحين صار مايضيف ما أدري وين المشكلة

مع اني ماغيرت ولاشي

الكود:

 Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click

        Dim con As New OleDbConnection
        con.ConnectionString = "provider =microsoft.jet.oledb.4.0;data source=c:\CBL\CBLDB.mdb"

        'retrive questions from database depend on exam
        Dim i As Integer

        con.Open()

        If exam = 9 Then

            Dim st As String = "select * from student"
            Dim studn(20) As String
            Dim studp(20) As String


            Dim coms As OleDbCommand
            coms = New OleDbCommand(st, con)
            Dim rs As OleDbDataReader
            rs = coms.ExecuteReader


            Dim k1 As Integer = 0

            While rs.Read

                studn(i) = rs.GetValue(1)
                studp(i) = rs.GetValue(2)

                If n <> studn(i) Then
                    If spass <> studp(i) Then
                        i = i + 1

                    Else
                        i = i + 1
                    End If

                ElseIf n = studn(i) And spass = studp(i) Then
                    k1 = k1 + 1
                    TextBox4.Text = rs.GetValue(0)
                    Exit While

                End If
            End While

            TextBox2.Text = Date.Today
            TextBox1.Text = "chapter 1"
            'TextBox3.Text = result.ToString
            con.Close()


            If k1 > 0 Then
                Try
                    Dim w As New OleDbCommand
                    w.Connection = con
                    w.CommandType = CommandType.Text
                    w.CommandText = "INSERT INTO exam(etype,edate,grade,SID)" & _
                   "values('" & TextBox1.Text & "','" & TextBox2.Text & "','" & TextBox3.Text & "','" & TextBox4.Text & "')"

                    con.Open()
                    w.ExecuteNonQuery()
                    con.Close()
                    MsgBox("تمت الإضافة بنجاح ")

                Catch ex As Exception
                    Exit Sub
                End Try
            End If
        End If
End Sub