PI Manual logger with laboratory data without exc/dev

Hi guys, 

Another obstacle for me in learning to use PI for my need.

I need to have exact data at exact time retrievable without any exception or compression.

Supposed I have LABDATA1 tag and I entered the data using PIPutVal, or PI Manual Logger.

How do I set the attribute or set the LABDATA1 so that when I retrieve the data, it will list

instead of 

21-AUG-13 00:00       23

22-AUG-13 00:00       23   ( no data but interpolated / show up from previous data)

I tried disable compression  and exception, without luck. it is adding numbers when it is not supposed to be an interpolation of data. 

Please help improve my understanding,

Thank you