Public Class Form1
 
    Dim startIndex As Integer = 0
    Dim words As String()
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        RichTextBox1.Text = "Autodefinida como un esfuerzo colaborativo por crear una enciclopedia gratis, libre y accesible por todos"
        words = RichTextBox1.Text.Split(New Char() {" "c, "."c, ","c, vbCr, vbLf}, StringSplitOptions.RemoveEmptyEntries)
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
 
        Static i As Integer
 
        startIndex = RichTextBox1.Find(words(i), IIf(i = 0, 0, startIndex + 1), RichTextBox1.Text.Length, RichTextBoxFinds.WholeWord)
 
        If startIndex > -1 Then
            RichTextBox1.Select(startIndex, words(i).Length)
            RichTextBox1.SelectionColor = Color.White
            RichTextBox1.SelectionBackColor = Color.Blue
        End If
 
        i += 1
    End Sub
End Class