Private Sub CallCurrentForm(ByVal pForm As String)
        'look whether form is already opened
        For Each openedform In Me.MdiChildren
            If openedform.Name = pForm Then
                vCurrentForm = openedform

  Dim MyExcel As New Excel.Application
        Dim wb As Excel.Workbook
        wb = MyExcel.Workbooks.Open("c:\backup\text.xls")
        Dim oleobjs = CType(wb.ActiveSheet.OleObjects, Excel.OLEObjects)
        oleobjs.Add(Link:=False, Filename:="c:\backup\test.doc")

Public Class Form1 
    Private ActiveTextBox As TextBox 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click 
        If ActiveTextBox IsNot Nothing Then

TextBox1.HideSelection = False 'can be set once in design time
       
         TextBox1.SelectionStart = TextBox1.Text.IndexOf(TextBox2.Text, StringComparison.OrdinalIgnoreCase)
        TextBox1.SelectionLength = TextBox2.Text.Length

 For Each dc As DataColumn In dt.Columns
            dc.ColumnMapping = MappingType.Attribute
        Next
        dt.WriteXml("c:\backup\test.xml")

 Private Function ISValidIP(ByVal IPAddress As String) As Boolean
        Dim validFormat As String = "\b(([01]?\d?\d|2[0-4]\d|25[0-5])\.){3}([01]?\d?\d|2[0-4]\d|25[0-5])\b"
        Dim rxn As System.Text.RegularExpressions.Regex = New System.Text.RegularExpressions.Regex(validFormat)
        If rxn.IsMatch(IPAddress) Then
            Return True