[O] nested macro expansion?

[Eric Abrahamsen]

What I'm trying to do is have a macro that takes the computed TIMESTAMP
property for an entry, and then runs it through a custom function that
breaks out the start/end times, and produces a nicely formatted string
from that.

I don't see how to write a macro that feeds the value of a computed
special property to a function.

Right now my testing version looks like this:

#+MACRO: bubba (eval (format-time-string "%Y" "$1"))

and I'm calling it like this:

{{{bubba({{{property(TIMESTAMP)}}})}}}

That doesn't expand the interior "{{{property(TIMESTAMP)}}}" clause.
What `format-time-string' ends up seeing is "{{{property(TIMESTAMP",
without the final braces etc.

Is there any way to get that value expanded first, and then passed to
`format-time-string' (or, eventually, my custom function)?

Thanks!

Eric