Highlight Certain Text Inside A RichTextBox ?

I am currently making a Syntax Highlighter.How can I highlight certain text inside a RichTextBox ? I am Currently Using This Code :

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)[code].....

but it will only Highlight 1 of the word I set / Change the whole text into the selected colour

Example :

'I wanted to Highlight "Hello"

'I put this code into RichTextBox_TextChanged:

Highlight("blue","Hello")

'And It will Only highlight The First "Hello" inside my Text :

'Hello my name is XXX, Hello

And, can I Highlight text between certain text / after certain text

Example :

'Highlight After the '
Or :

<!-- Highlight between these 2 tags -->