[Orgmode] Babel - display results in an overlay?

[Taru Karttunen]

Hello

I am looking for an org-mode solution to storing a number of variables and
referencing them nicely in an org-mode buffer.

I would like to write something like this:
"{foo:1+3} and {bar:foo+3}"
and have it displayed (with overlays) as:
"foo:4 and bar:7"

Any ideas how to hack org and babel to do this. Simple numeric
operations suffice but I have a few dozen variables so an easy
an intuitive interface is the most important aspect.

- Taru Karttunen