Depending on the current the valve needs, you could amplify the 5 V from the PCI-6023E with an amplifier circuit to get 24 V.
You could also get a relay that you can control with the digital lines of the PCI-6023E. Get an external power supply that can give the 24 V and use the digital line controlling the relay to programmatically turn the valve on/off. I hope this helps.
Regards,
Todd D.
National Instruments
Applications Engineer