Change build command based on context of build request

I have a project with unit tests. I want to use ST2's build feature to run the unit tests, but I want to be able to click on a test in ST2, run the build command with my caret on the test case, and have ST2 run only that test case. (If the caret is not on a test case, then it should run all tests.) I can implement this logic myself, but the build system needs to know where the caret is when the build was requested. Can you pass this information?