Any way to kick off a Run configuration with a dynamic ENV var? (think: Kiwi single test)

I would like to be able to specify the KW_SPEC argument to a test case run configuration, so that I can run just one test instead of the whole file.  
In the case of Kiwi, this would mean providing a <filename>:<linenumber> for KW_SPEC.

I can't see any way to do this in AppCode so far... Is there a way it can be macro'ed?  A small plugin (perhaps using LivePlugin)?