Suresh:
Kai posted a current limiting circuit for a lamp driver in your lamp thread. You asked how it worked. I gave you a simplified exlpanation . Did you read it?
That circuit with the correct emitter resistor would work here. The micro portion is not needed simply connect the input resistor to the base of the driver transistor to a 5v supply.
The actual collector current will be lower than the emitter current by the actual base current of your transistor. Suitable testing and selection will give you a very accurate current for short term testing.
If you want long term accuracy and stability you must know what you need to achieve before you start designing. As yet you have not supplied even rudementary specifications to allow us to guide you towards a design that has a chance of meeting the test's required accuracy specification.
Have you looked for a suitable basic electronics text to assist you in understanding the questions that you ask? Terry