Reset custom region in winforms using C#

Question

i have removed left portion of a form using graphics path and region command. when i am trying to show group box on removed portion, group box not appeared. how do i show the groupbox on removed region area ?. or how do i reset the region

GraphicsPath shape = new GraphicsPath();  
shape.AddRectangle(new Rectangle(200, 0, FormWidth, FormHeight));  
this.Region = new Region(shape);