Hi:
Generally, when folks define a hyperlink in PROC REPORT and that hyperlink goes to another page, that -is- considered a "drill-down" even if the original link is drilling down to a new HTML page. That is the most common form of static drill-down available out of the box with PROC REPORT -- the URL= option.
The type of "expanding" information you describe sounds like dynamic HTML or HTML with embedded Javascript or possibly PHP or ???? It almost sounds to me like you want the HTML page to act like an Excel Pivot Table. I believe you will either:
1) have to code the JavaScript/DHTML/PHP yourself by modifying the HTML4 tagset template (or using techniques such as the one discussed here:
http://support.sas.com/kb/24/068.html
or
2) if this type of drill-down behavior is possible with XML and an XSL transform, then code a custom XML tagset template and a custom XSL transform
or
3) create an Excel Pivot Table out of your report data (I believe this is possible using the TAGSETS.TABLEEDITOR destination, which creates HTML with embedded JavaScript to enable the HTML file to be opened in Excel.
http://support.sas.com/rnd/base/ods/odsmarkup/tableeditor/index.html )
With the SAS Add-in for Microsoft Office, you could build your Pivot Table directly from a SAS data source. But, the SAS Add-in is part of the Platform for Business Analytics. And, of course, the Platform also has OLAP cube capability, which also has the kind of expansion and drill-down features that you describe.
cynthia