Hi,
this is a high side current source. It regulates so that between OUT and ADJ is 1.25V.
For a good regulation you can use a open collector current source to Gnd, that is controlled by your 0..1V signal.( simple Opamp circuit)
Now put a second resistor in the line to ADJ.
Also connect the open collector to the ADJ pin.
What values to use:
Lets assume that the current source regulates 0..10mA with 0..1V input.
This means you need a 100 Ohms resistor at the emitter.
The usual current setup resister should be used to supply 1A. This means 1.25 Ohms.
The additional resistor is: (1.25V - 0.35A * 1.25 Ohms) / 10mA = 81.25 Ohms.
Now with 0 V you get 1A, and linearely decreasing to 350 mA with 1V.
Hope this helps.
Klaus