/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.

Oops, sorry, Scheme has

((eval (string->symbol "foo")) arg1 arg2 ...)

Therefore, my challenge has no solutions in either CL or Scheme.