questions about plotting indicators?

[p <rhodes@xxxxxxxxxxxxxx>]

  Have a question about how to plot 2 indicators only on the last 20 days
of a chart.
  Like if I have 500 days of data on my chart.  How can I have a plot of
say a moving average and say something like stochastics or RSI plot only on
the last 20 days?  
  Any ideas, would be helpful.

  Thanks