Diy user definied Constant current power source

[svarbanu]

Could any one post a circuit where the user feeds the required ampere of constant current? output range is 1 milliA to 15 milliA and 10 to 30 Vdc.

I have made a circuit with lm317 and variable resistor to achieve the output range but i need some kind of input mechanism and feedback circuit to maintain the constant amperes for automating this.