In case it is useful for anyone else, in the wikibook I've written a new article describing a technique I use when writing a lot of rules for OpenClinica .
As the introduction goes:
"If you want to write more than a few rules, and don't want to set up the
Rules Designer app, it is possible to make life a little easier using
the xml tools available in Excel 2010. This method takes advantage of
OpenClinica's xsd schema used to validate rule xml files to guide Excel
into providing an interface for working with rule xml data."
So basically if you are comfortable writing rules in plain xml, using Excel in the way described makes the process a bit easier to handle.