This map sample shows how to suppress nodes inside a map by passing false from a logical functoid. The blog post below gives more detail on the sample.
The mapper in BizTalk 2004 makes it easy to suppress nodes inside the mapper. The key is to send the looping node a "false" from a Logical Functoid. I have tried sending a Boolean False value from a Scripting Functoid but that was unsuccessful.
Get more information from the original blog post on this topic: http://www.biztalkgurus.com/blogs/biztalk/archive/2005/01/27/How-to-Suppress-Nodes-In-the-BizTalk-Mapper.aspx