Draw rectangle between selected datapoints

I want to add rectangle to my ultrachart between 2 selected datapoints like below;

I can get the rows by ChartDataClicked Event. Thats okey. However i can not draw the rectange between 2 points.

I think i should use 'FillSceneGraph' or 'Annotains'. However no idea about how to do it ?

Can you help me abou this ?