Method to cycle voltage?
You probably don't want to use a LM317 as you're close to the reference voltage, which is between 1.20V and 1.30V, so the error in your output could (1.4/1.25)*0.05V = 0.056V, which together with a 5% resistor divider error (0.07V) could put you outside the +/-0.1V tolerance on the 1.4V. 

1.4V/33R = 42mA, so there are many fixed LDO regulators which will take 5V ( either from arduino or another fixed regulator ) and output 1.4V. Some have an enable pin as mentioned in this LD6836 datasheet which either enables 1.4V or sets the output to high impedance, so switching is easier than with three-terminal regulator.