Hi,
I'm assuming that you have a NI DAQ card. There are some VB examples that should've been installed with NI-DAQmx by default (if you installed DAQmx after installing VB6). Take a look at the example code in your National Instruments directory (eg. C:\Program Files\National Instruments\NI-DAQ\Examples\Visual Basic 6.0\Analog In\Measure Voltage\Acq-Int Clk).
Let me know if you have any questions.
Way S.
NI-UK Applications Engineer