Javascript problem in AJAX

Iam trying to build a 'dyanamic double combo' (where the second
combobox gets populated upon the selection of items in first). The
second combobox has atmost 20-25 entries. Out of these 4-5 entries are
static and the rest are to be filled from the database. Iam using plain
text instead of XML.

Can't innerHTML be used to populate a combobox? Do I need to use
options[] instead? If so, then do I need to use XML for that? Can it be
done without XML?

Here is a sample of what Iam doing:

if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
{
document.getElementById("idofsecondcombobox").inne rHTML=xmlHttp.responseText

}
}

Then in my asp file I use something like:

<% Response.write " <option selected value='1'>Choice1</option>"%>
<% Response.write " <option value='2'>Choice2</option>"%>
<% Response.write " <option value='3'>Choice3</option>"%>
<%for i = 0 to count-1%>
<% Response.write " <option value='"Array(i)&"'>Choice"&
Array(i)&"</option>"%>
<%Next%>

This is just a part of the code but the problem is that it isn't
working. Any suggestions plz?