Thanks for reply PaulS/Knut_ny. It motivates me to contribute more to community.. 
Got the information. But wonder, why this (using timer instead of Index ++ for every loop runs)
>>That's a far better idea.
I have an argument with my colleague who said, it not much difference between index++ and using timer (Micros() / Millis()).
Any thought?
Further, I agree, it is not easy to say - how much time the the loop takes for each. Assuming there is no delay statement in side main loop. Wondering, whether, using INLINE function will help to execute the function faster? ( I am using FIO)
Cheers! 
Chandra