ช่วยดู code update หน่อยครับ พอกดแก้ไขแล้วมันขึ้น incorrect syntax near '.....'....... Vb.net

'update button
    Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
        Dim update_Constr As String = "Data Source=KWAN-PC\SQLEXPRESS;Initial Catalog=Chqprint;Integrated Security=True"
        Dim update_Comstr As String
        Dim update_Con As SqlConnection
        Dim update_Com As SqlCommand
        If TextBox1.Text <> "" AndAlso TextBox2.Text <> "" AndAlso TextBox3.Text <> "" AndAlso TextBox4.Text <> "" Then
            update_Comstr = "UPDATE customer SET cus_name = '" & TextBox2.Text & "," & _
                "cus_position=" & "'" & TextBox3.Text & "'" & "," & _
                "cus_remark=" & "'" & TextBox4.Text & "'" & "," & _
                "WHERE cus_id =" & TextBox1.Text & " ; "
            'MsgBox(cmdUpdate.CommandText)
            update_Con = New SqlConnection(update_Constr)
            update_Com = New SqlCommand(update_Comstr, update_Con)
            update_Con.Open()
            Try
                update_Com.ExecuteNonQuery()
                MsgBox("ทำการแก้ไขข้อมูลเสร็จเรียบร้อย.", MsgBoxStyle.Information, "Edit Registration")
            Catch ex As SqlException
                MsgBox(ex.Message)
            End Try
        End If
        update_Con.Close()
        fill_listview()
    End Sub