The groupbox is created like this:

$GroupBox = $Form.GroupBox()

Then the controls that appear inside the groupbox, are created as "children" of the groupbox, like this:

$Button = $GroupBox.Button()

The bounds of the button (Left,Top,Width,Height) are then specified in client co-ordinates (relative to the parent GroupBox), for example to position the button in the top left corner of the GroupBox ...

$Button.Location = 0,0

-Shawn