[flexcoders] Create border for inner subgrids within a grid - How?

[pbrendanc]

Another noob question - I've created a dynamic (n*n) grid and need to
provide some visual delineation of the inner grids - e.g. a 4*4 grid
contains 4 inner 2*2 subgrids.

How can I create a border around each of these subgrids?  (This  will
also need to be done dynamically).

TIA,
Patrick

FWIW - The grid is built with the following function

private function buildGrid (nrows:uint,ncols:uint):void {

                 for (var i:Number = 0; i<nrows; i++) {
                     var myGridRow:GridRow =  new GridRow();
                     // for each col add child controls
                     for (var j:Number = 0; j<ncols; j++) {
                         var myGridItem:GridItem =  new GridItem();
                         myGridItem.addChild (myBtn);
                         //Add cell to row
                         myGridRow.addChild (myGridItem);
                     }        // end col loop

                     // Add row to grid
                     myGrid.addChild(myGridRow);
                 }
                 // Add grid to parent container (canvas/form/panel
etc??)
                 mypanel.addChild(myGrid);
}