Rosamond Kember (the Research Assistant responsible for most of the work on the SituationENGINE) recommends this tutorial to assist in creating User Interface elements in CryENGINE3:
It's split into 2 half hour tutorials...
which is quite long but the author seems to go through all the necessary steps - creating a button in flash
with dynamic text, the xml files you need to create and where to put them, and
the set up in flowgraph.
Cheers