Color Text In RichTextBox Object

I want do a syntaxhighlighter in richtextbox. Example RichtextBox content:

function veri()
{
var numara = 1;
for (i=0; i<100; i+=numara){document.write(i)}
}

I want make "function", "var", "if" ... etc words make blue. Is there any function in VB like Replace for richtextbox (i can use color)

I coded this but not performed for long strings:

Dim son_yer As Integer = 1
If RichTextBox1.Text <> "" Then
Do While InStr(son_yer, RichTextBox1.Text, kelime) > 0

[Code].....