Use previous bar's available cash for position sizing


I am testing a rotational equity strategy. What I am trying to do is use previous bar's available cash for next day's position sizing. Is there any way I can easily access the available cash as an array like Equity array without resort to Custom Backtester?

I switched backtest report to Detailed log. I noticed there are values for Market Value, Equity, Cash. The question is how to access them in AFL.

I searched for this topic. I found the following posts. But they didn't address my issue.

If I can only do this via Custom Backtester. Can anyone with experience please give me an example? I read the document for Custom Backtest

There is a 'double Cash', but I do not know how to use it. Can any one point me an similar example about how to use it? Thank you very much. You help is very appreciated.