Can someone please modify this Supply and Demand Area to include a Back Limit adjust

sharingan9
62
sharingan9  

Can someone please modify this Supply and Demand Zone indicator to include a Back Limit adjust. It plots supply and demand areas and when I have it on many charts it slows my MT4 down but its such a useful indicator. Please add a Back Limit so I can say only display zones for the last 300 candles for example. Thanks in advance

myname
3231
myname  

It uses zigzag (metatrader zigzag recalculates all the bars all the time)