Note: This article has done its job, and will be retiring soon. To prevent "Page not found" woes, we're removing links we know about. If you've created links to this page, please remove them, and together we'll keep the web connected.
A custom Lists tool can be set up to allow workspace members to add only one item to the tool. This feature is useful in cases in which you want members to fill out a single item, such as a Person form in an address book.
Enter the Designer.
Click Settings and Options and then click the Settings tab.
Check Limit one item per member.