This is definitely not possible with the current dtml-in tag. The dtml-tag does not provide "reverse_expr=", "sort_expr=", and so forth (like to the dtml-tree tag).
On the contrary, you can use sort_expr with dtml-in. Look at the following method: <dtml-unless sort_by> <dtml-call "REQUEST.set('sort_by','title')"> </dtml-unless> <dtml-in Catalog_Org size=50 start=query_start sort_expr="sort_by"> <dtml-if sequence-start> <dtml-if previous-sequence> ... ... ... <table width="95%"> <tr valign="top"> <td><b>Name<br><img src="/img/sp_white.gif" width="1" height="6"></b></td> <td><b><a href="org_list?sort_by=title&facility_type=&dtml-facility_type;&org_type=&dtml-org_type;">Organisation <dtml-if "sort_by=='title'"> <img src="/img/arrow_down" border="0"> </dtml-if> </a></b></td> <td><b><a href="org_list?sort_by=city&facility_type=&dtml-facility_type;&org_type=&dtml-org_type;">City <dtml-if "sort_by=='city'"> <img src="/img/arrow_down" border="0"> </dtml-if> </a></b></td> </tr> ... ... ... -- Milos Prudek