0 - 10 VDC to 4 - 20 mA conversion

OK, this one should be pretty simple. Does anyone have
a quick and dirty circuit that will convert a 0 to 10
VDC output on my DAC to the required 4 to 20 mA input
signal (input impedence of 250 ohms) on my VFD? And no,
I do not have control of the DAC!

V = IR
1 volt = (0.004 Amps)(250 ohms)
5 volt = (0.020 Amps)(250 ohms)

Believe it or not, this is the first time I've actually
run into a situation like this. I've done a fair amount
of digital design, but when integrating with the outside
world in was always with control over a DAC (etc) and
have been going into 2K plus impedence. This project is
retrofitting a new VFD to an existing CNC control. As
such, I don't have any ability to control the DAC.

Thanks,
Alan