This is the bane of using Dreamweaver Templates ;). The work around to this error is to manually detach the page from the template temporarily, make the change, then reattach the template to the page.
You will need to use an external text editor for this.
close Dreamweaver and open the template in another text editor like note pad.
The line that attaches the template to the page will look like:
<html xmlns="http://www.w3.org/1999/xhtml"><!-- InstanceBegin template="/Templates/siteassistpro_template.dwt.asp" codeOutsideHTMLIsLocked="false" -->
Remove the '<!-- InstanceBegin template="/Templates/siteassistpro_template.dwt.asp" codeOutsideHTMLIsLocked="false" -->" part:
<html xmlns="http://www.w3.org/1999/xhtml">
This will detach the page from the template.
You can open Dreamweaver and make the change to the recordset. After changing the recordset, open the page in your text editor again and add back the template code.