"Classpath to add Groovy Modules"

I'd like to use the HTTPBuilder Groovy modules, and while my groovy script works within Groovy, RapidMiner5 does not find the actual classes in the jar files.  In  RAPIDMINDER_HOME (on my machine set to c:\program files\rapid-i\rapidminer5\) I found a groovy-all.jar that seems to contain all class files that groovy needs.  Do I actually need to add my module to this .jar file (thus performing surgery on a number of other .jar files to get one encompassing "groovy-all.jar" file) or ...

may I set a classpath somewhere that "Execute Script" through RapidMinder would then read prior to execution so my classes would be found?