On the web you can control section expanding by passing an operator in the URL.
In the DominoPDF installation you can find a PDF named URL Cheat Sheet which details all the options for Domino URLs, including expanding sections etc.
(You can also find it on the web here http://www-128.ibm.com/developerworks/lotus/library/ls-Domino_URL_cheat_sheet/)
As an example;
To collapse a section
http://domain/test.nsf/section?ReadForm&ExpandSection=-1,-2
To expand a section
http://domain/test.nsf/section?ReadForm&ExpandSection=1,2