Cannot reference data far back enough

[naifwonder]

I am working on a system which references a certain amount of bars prior to the current bar to make certain calculations. The strategy only allows me to reference up to twenty bars ago. For example, if I use Close[20], I get the value for the close of the bar that occurred 20 bars ago. However, if I use Close[21], it is not defined (it is undefined for any value past 20). Is there a limit on how many bars back a strategy can reference, and if so, is there any way to get around it?

[NinjaTrader_Ray]

You can reference as far as you have historica data for. If you reference Close[21] and data does not exist for this then you will get an out of index error and your strategy will terminate and an error message is throw to the Log tab.