HTML DOM questions

I have the following questions:

I have a textbox with this text:
<html>
<head>
<title>Untitled</title></head>
<body>
</body>
</html>

After that i set the document html of a DHTMLEdit Control to this text

dhtmledit1.documenthtml=editbox.text

1.Can i from the DOM of the DHTMLEdit control get also the comment tags?
2.I want to get the html between two comments that are
 and  how do i do this with the
DOM ?
3.I want to use the DHTMLEdit control to alter the document title of a webpage
i try
dhtmledit1.dom.title="HELLO" but nothing happens !
I check the dhtmledit1.dom. and it somewhere exists but when i try
to make
editbox.text=dhtmledit1.documenthtml
it does not alter and remains "Untitled"

4. How do i alter the html between a tag . For example the <head> tag .
5.How do i get the position of a tag item within the document html (for example it is the 40th character
from the start)

thanks!