Evilopinions

I am trying to build a labview program that can tune the frequency of a function generator to a user specified frequency.I am hoping that the tuning tolerance be better than 1 percent.Only want to tune between 1 and 40KHZ. Should have one analogue input in order to read the frequency and one analog output to control the frequency. Any pointers ? Any ideas ? Any source code or modules that I can build up on ? Thanks in advance for your help//