Well, im not entirely sure what you mean but i think i know.. Try this as a starting point.


Code:
        
Dim Reader As New StreamReader("C:/email.txt")
        Dim Line As String = Reader.ReadLine()
        Do Until Reader.EndOfStream = True

            If Line.Contains("some word") AndAlso Not Me.TextBox1.Text.Contains(Line) Then
                Me.TextBox1.AppendText(Line + vbNewLine)
                'TextBox1.AppendText(Line) = TextBox1.Text + Line & Environment.NewLine
                TextBox1.SelectionLength = TextBox1.Text.Length
                TextBox1.ScrollToCaret()
            End If
            Line = Reader.ReadLine
        Loop
        Reader.Close()