[CMake] Extending a target??

[Doug Reiland]

Is there anything to "add to" a target after it is declared?

For example,

add_library(foo STATIC foo1.c foo2.c)

....

add_some_more(foo foo3.c)
or
add_some_more(foo foo3.o)

If not, feasibility on how it could be implemented?

Thanks,
Doug