Resizable panels

I have a form with a richtext box and an webbrowser control side by side. The richtextbox is on the left, the webbrowser control is on the right. I want to be able to have the separator between the two controls be adjustable so that when I move it to the left, the width of the richtextbox gets smaller while the width of the webbrowser increases, and when I move it to the right the width of the richtextbox increases while the width of the webbrowser decreased.

When I increase the form's height, I want both the control's width to increase in side in proportion as well.

Any ideas on how to do something like this?

Have you looked at the Dock and Anchor properties? Also, the behavior you describe is a bit odd. Why would one control get smaller as you expand the size of the form? I can understand it staying the same size and another control growing, but don't you think that one control growing while another simultaneously shrinks is weird and unexpected behavior?