I think you will need a library that interfaces with your GUI. SWT provides context-sensitive help for Eclipse plug-ins but I don't know how it works when you use SWT outside of Eclipse.
The online Eclipse documention seems to make a weird use of frames so I don't know how a screen reader would navigate it. I think what you want is something called Data Tools Platform Help-Helper Documentataion which is a section in the DAta Tools Platform Plug-in Developer Guide.
Susan
