Previous Bollinger value

[Mike2]

I have an efs which shows historical results of bollinger bands.

I want to be able to measure results based on the previous bar's values.

I can get this to work in real time using
if (getBarState() == BARSTATE_NEWBAR) UpperPrevious = Upper;

However, if I try using
UpperPrevious = Upper(-1);
I get no result.

My premain is
var studybb = new BollingerStudy(20, "Close", 2.0);
and in main I have
var Upper = studybb.getValue(BollingerStudy.UPPER);

Is there a way to get the previous bollinger value to be used for calculations whilst drawing the study ?.

[ACM]

Mike2
Use studybb.getValue(BollingerStudy.UPPER,-nn); where -nn is the number of bars back you want to retrieve
Alex