Add an expand All or collapse all button to the parentheader

Question

I have a basic HierarchyChildTemplate grid with parent and hild relation ship defined and the grid works fine. One of the requirements it to add a plus button in the header for the first column when clicked by the user it has to expand all the rows with row details and collpase when clicked again just like it would behave for each row.

I was able to add a button and expand the rows details successfully but I need the button to show up in the row header.