Hello,
Your application could be done much easier if you switch to DAQmx. The functions you will need to use are the following (in this order):
DAQmxCreateAIVoltageChan [Specify your four channels here]
DAQmxCfgSampClkTiming [Specify the Rate, Samples per channel, and finite acquisition]
DAQmxCfgAnlgEdgeRefTrig [ Specify the source of your AI trigger, slope, level and pre-triggered samples)
DAQmxStartTask
DAQmxReadAnalogF64 [Specify here the timeout and Read your values]
DAQmxClearTask
Hope this helps,
LA