Michael,
You may find
this link a little more helpful. It uses our new NI-DAQmx driver, as opposed to our older Traditional (Legacy) NI-DAQ driver. The example in the link has a "Rate" control, which sets your sample rate. Also, this
KnowledgeBase article does a bit better job of explaining the process used in the above example. The KB also has an example attached.
Please let us know if you have any questions about this process. Note that it is a bit of a hack, and not representative of the usually very clean and efficient DAQmx code.
Hope this helps,
Ryan Verret
Product Marketing Engineer
Signal Generators
National Instruments