[SWT] Vertically expandable Composite

Question

Hi,

I'm building an SWT UI, and it has a window (Shell) with three Composites stacked one below the other. I want that:

1. all to expand to the maximum possible width (width of the window)
2. the first and third Composites have a height of 100px each
3. the third composite expand to a height of height_of_parent - 200px - any_margins_or_paddings.

Objective 2 is trivial, and I did Objective 1 using the ColumnLayout defined here.

How do impolement Objective 3?
Many thanks :)

PS: I'm very new to SWT.