@thatblokedave it works good if the data source is csv,but what happen if the datasource is real time data,may be the return data0 and data1 is not equal

@alexgorbachev at last ,it prove it is works,but there some thing to say,if your extend num>=2,
the extend in bstart and bupdate must be define and inplement by strict sort,it seem the backtrader recoginze them by order and not name

i have a try but it works not what i wanted,the extra cannot be update auto