messagebox for validation onrowupdating in gridview

[aqua62]

Protected Sub GridView1_RowUpdating(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewUpdateEventArgs) Handles GridView1.RowUpdating

        ' ''Dim role1 As String

        ' ''role1 = e.NewValues(0).ToString

        'string myLastName = e.NewValues[1].ToString();



        ' Dim tb As TextBox = GridView1.Rows.Item(e.RowIndex).FindControl("txt_role")

        'Dim role_name As String

        'role_name = tb.Text


        Dim str1, str2 As String
        Dim ds1, ds2 As New DataSet

        lobId = DropDownList1.SelectedItem.Value
        duId = DropDownList2.SelectedItem.Value
        projectId = DropDownList3.SelectedItem.Value
        roleId = DropDownList4.SelectedItem.Value




        Dim sID As String = GridView1.DataKeys(e.RowIndex).Values(0).ToString

        Dim txt_role As TextBox = CType(GridView1.Rows.Item(e.RowIndex).FindControl("txt_role"), TextBox)

        Dim rolename As String = Convert.ToString(txt_role.Text)
        GridView1.EditIndex = -1
        GridView1.DataBind()

        Dim cnt As Integer
        str1 = "SELECT COUNT(*) FROM role  WHERE (role = '" & rolename & "' and role.project_id='" & projectId & "' )"


        da1 = New SqlDataAdapter(str1, con)
        da1.Fill(ds1)
        cnt = (ds1.Tables(0).Rows(0).Item(0))

        If (cnt >= 1) Then
            'flag = True

            MsgBox("role exists, enter different")

            txt_role.Text = ""
            txt_role.Focus()

            Exit Sub

        Else
            'GridView1.UpdateRow(0, True)

            str2 = "update role set role = '" & rolename & "'   where  role_id = '" & roleId & "' and  project_id = '" & projectId & "' "

            da2 = New SqlDataAdapter(str2, con)
            da2.Fill(ds2)

        End If


    End Sub

I want to check that the same role is not entered, but the problem is that it displays the messagebox on repitition of values but still updates the repeated values in the database