Not exactly sure what you want to do, but a good place to start would be to get familiar with LVSpeak (Non-NI supported plugin for LabVIEW using LabVIEW Scripting and the Microsoft Speech SDK). You can either use this plugin or use the ideas of the plugin to create a program that interfaces with a standard Serial read/write VI (Check out the example finder for a great place to start).
By the way, you might want to try posting this on the correct board. LabVIEW is probably the most likely place for this question, and with Instrument Control being the second, but definitely not Digital I/O.
