Question about controlling a device with 4 to 20mA input current.

I have some air valves that take a 4-20mA input signal to adjust the output pressure. The valves also have 1-5 V output voltage tied to an internal pressure transducer. Is there a way to add an additional circuit to an analog output that would allow me to send a 4-20mA signal to the valve? I guess I'm looking to take a variable voltage from the labjack and convert it to 4-20mA variable current.  Thanks in advance!