Equivalent to VPATH for searching for Makefiles?

[Garrett Cooper]

Hi guys,
     I realize that using --include can do this, but is there a way to
tell make how to do this for Makefiles as well from within other
Makefiles (VPATH doesn't work ;P)? It would be a really cool
enhancement to have, if it doesn't already exist, as it would make
ginormous make projects simpler by setting a default `search path' for
Makefiles that get included.
-Garrett