[plt-scheme] abstracting over (PLaneT) requires

Is there any way to abstract over requires?  In particular, I'm
interested in abstracting over the version of a PLaneT package that I
require.  Something like

  (require (planet "some-file.ss" ("joe" "a-package.plt" MAJOR (= MINOR))))

where MAJOR and MINOR could be bound in exactly one spot.  Thus, I
could easily do a system-wide change of which version of a-package.plt
I am including.

Thanks!

Rob