If you are using Java 6 or higher you can use wildcards of this form:
java -classpath ".;c:\mylibs\*;c:\extlibs\*" MyApp
If you would like to add all subdirectories: lib\a\, lib\b\, lib\c\, there is no mechanism for this in except:
java -classpath ".;c:\lib\a\*;c:\lib\b\*;c:\lib\c\*" MyApp
There is nothing like lib\*\* or lib\** wildcard for the kind of job you want to be done.