nmac on Convert counter values to rate

3 days to search .... but no result! 

Every minutes i've a counter value in a chanel.
How can i find a value (juste one !) one (year, day or hour) before ?

% For 'now' it's ok
Data1 = thingSpeakRead(202xxx,'Fields', 4, 'ReadKey','1F16B5PPNYxxxxxx');

% don't working for (year, day or hour) before
[Data2, time] = thingSpeakRead(202xxx,'Fields', 4, 'DateRange', [start, stop],'ReadKey','1F16B5PPNYxxxxxx');

Thank to you for help

Nicolas