/prog/ challenge

Write a macro that, given a term of code, transforms all the calls to the function FOO in that term, and only those calls, into calls to function BAR with the same arguments.
Language: Common Lisp or Scheme.

>>40
I think a reasonable definition for Common Lisp would be (funcall (function foo) ...) (foo ...) and maybe even (apply (function foo) ...).

That's what I took OP's challenge to mean.