How to make a port not build

[Derrick Ryalls]

Normally when building a port, I just type make install clean and let it
run.  However, I need to modify a source file before the build starts.
Since many patches are included in the port, I am looking for it to stop
after everything is downloaded extracted and patched, just before the
build starts.  Is there an elegant way of doing this besides hitting
Cntrl-C when it starts to build?

-Derrick