Use writer or use CI?

[eluser]Unknown[/eluser]
Windows 2003+IIS 6.0+PHP+ISAPI Rewriter

I'v already build my website.
My website's URL like http://www.example.com/book-htm-txt_id-test.html
my ISAPI rewriter: RewriteRule ^(.*)-htm-(.*)\.html$ $1.php?$2

and the reult:
book.php?txt_id-test

I parse it:

Code:

$query_str = $_SERVER["QUERY_STRING"];
@$query_str_arr = explode("-", $query_str);
$count_num=0;
for($i=0;$i<Count($query_str_arr);$i+=2){
@$_GET["$query_str_arr[$i]"]=$query_str_arr[$i+1];

so _GET["txt_id"]=test

How I can do it in CI,use Rewriter or use CI.
not change former URL also use CI Framework