As an FYI, this is covered in the Getting Started with the MSP430 Workshop. Searching the workbook for "even_in", you should find it discussed in the interrupts chapter (page 5-25 in version 3.02a of the workshop).
You can find this workshop on its wiki page: http://processors.wiki.ti.com/index.php/Getting_Started_with_the_MSP430_LaunchPad_Workshop