Hi pokiri,
Your application belongs much closer to metrology field. What you want it's not easy to achieve. Bear in mind that you must provide special input guard circuit in order to maintains accuracy by minimising the effect of probe or cable leakage.
If I well understand you want one digitally controlled potentiometer in 1 mili ohms increment. You'll apply a voltage across the pot and then throgh the cursor, fed a DVM's input that you want to calibrate ?
If that you have in mind, we can find a better solution in order to avoid expensive and high accuracy resistance bridge. Please come back with an enhanced description of your application.
Regards,
Silvio