http://wiki.lazarus.freepascal.org/TAChart_Tutorial:_Dual_y_axis,_Legend
You mean CandleStick? Yes, use TOpenHighLowCloseSeries and set its Mode to mCandleStick. There is a demo in folder components/tachart/demo/financial of your Lazarus installation.
The information that you provide is too unclear to give you more detailed help. What is "currentmarket"? Why are you calling form6 explicitely? What is happening before the .Clear?. I only can repeat: try to reduce the issue to a small project which shows the issue and which you can upload here. When doing this you normally find the issue by yourself, or - if not - I have something to work with.
currentmarket is a OpenHighLowlCloseserie.Since OpenHighLowCloseSeries requires several y values (4 to be specific) I could imagine that you did not set the YCount of the chartsource accordingly. For this interal ListChartSource, this is done automatically, but maybe you are using an external ChartSource - all these details are important, and become clear when you post a compilable demo.
how i could intercept errors on charts? E:????Unit TAChartUtils declares the basic chart Exception: EChartError
another question: can i force the Y axis to use always complete numbers? IE 0,00000001, not a notational oneWhat is a "complete number"? What is a "notational" number?