HeX

Hi all,
I am writing a program which is similar to Microsoft's Paint. In order to draw the shapes, I am using vectors. However, I have a problem because when I draw a line and then a circle over the line, after the panel repaints, the line comes over the circle.
Can anyone tell me how to avoid this. I mean that the object that is drawn first on the panel should stay in the back when other objects are drawn after it and not come to front.