Probably not much help, as I'm not familiar with Rumba, but from their white paper:
VBA-type scripting support
Enables automation via scripting to improve end-user
productivity and streamline business processes. Supports the
execution of existing Micro Focus OnWeb Web-to-Host,
ViewNow, and/or competitive scripts on the Micro Focus
Micro Focus RUMBA PC-to-Host platform, reducing the
administrative costs associated with multi-client-type
installations and consolidations.
Custom application development
Support for EHLLAPI and COM interfaces provides maximum
flexibility and convenience for programmers, developers,
and other IT professionals.