You can not use the ADCIN with the comparators. ADCIN is for the ADC.
On my project i dont want to know whether the output is low or high but i want to know exactly magnitude of output voltage
Again, you can not use the comparators for what you want without doing some tricks which I told you about in my first reply. The peripheral to use for measuring the actual voltage is the Analog to Digital converter (ADC) for which the ADCIN command works.

Why have you are you obsessing on the comparators? What am I missing?