[plt-scheme] Help with units?

Hi folks,

I need some help with units. Conceptually I think I understand them,
but I am just not getting the details at all.

I want to define two units: parser-actions^ and parser^.

There is one unit that parses the data (parser), and there are two
parser-action units: one to generate text and one to generate latex.
At runtime, I need to create a parser, specify its actions, and at the
same time tell the parser-actions to use that parser to continue
parsing.

Is this possible? Is this the right approach?

Reading the documentation I guess that I am totally missing the point
about how to link units.