Test for readiness within Makefile?

[Felipe Gasper]

Hello,

        Is it possible, in a Makefile, to filter a list of paths by 
outdatedness?

        For example, if I have 

TARGET_JS=foo.min.js bar.min.js baz.min.js

… is there some way to make an OUTDATED_JS list that would contain *just* the 
members of TARGET_JS that are outdated?

        Thank you!

cheers,
-Felipe Gasper