How to Highlight Text

I can't use that code because I'm making a syntax highlighter.

After highlighting the rest of the words will become the color and it highlight the keyword.

If i type anything else it will replace the highlighted word.

I think my code works fine. I was just trying to give you the general idea. But to make it even more clear,I'll integrate my code with yours:

Public Function Highlight(ByVal highlightcolor As String, ByVal ParamArray WordsToFind() As Object)
        'Loop through all the words you specified:
        For i As Integer = 0 To UBound(WordsToFind)
            Dim Keyword As String = WordsToFind(i)
            'Determine which color the word must become:
            Dim currentPositionOfCursor As Int32 = 0
            Do
                Dim posOfNextHit As Int32 = RichTextBox1.Find(Keyword, currentPositionOfCursor, RichTextBoxFinds.None)
                If posOfNextHit >= currentPositionOfCursor Then
                    Select Case highlightcolor
                        Case "red"
                            RichTextBox1.SelectionColor = Color.Red
                        Case "blue"
                            RichTextBox1.SelectionColor = Color.Blue
                        Case "green"
                            RichTextBox1.SelectionColor = Color.Green
                    End Select
                    RichTextBox1.Select(posOfNextHit, Keyword.Length)
                    currentPositionOfCursor = posOfNextHit + 1
                    'reset the selection
                    RichTextBox1.SelectionLength = 0
                Else : Exit Do
                End If
            Loop
        Next i
        Return 1
    End Function