Maybe I should have asked the op - Is this for external voltage that you are tring to monitor, OR are you just tring to monitor/record the voltages from your PSU.
If External voltages, then follow my advise.
If Internal PSU voltages are what you are tring to Monitor, Follow saint19's advise. I normally use CPUID's HWMonitor. Note: HWMonitor does not report the +%, or +12 V correctly on my Gigabyte P55-UM4P (otheres have also reported incorrect readings)