  A prototype device capable of moving a radioactive calibration source to
multiple positions was operated at millikelvin temperatures using a modified
commercial stepper motor. It was developed as an in-situ calibration strategy
for cryogenic dark matter detectors. Data taken by scanning a calibration
source across multiple radial positions of a prototype dark matter detector
demonstrated its functionality. Construction, heat load, and operation of the
device are discussed, as is the effect of the motor on the detector operation.
A sample dataset taken over multiple positions of a SuperCDMS detector is
presented as an example of the utility of such a device.
