oldunits = get(ax(1), 'Units');
oldpos = get(ax(1), 'Position');
set(ax(1), 'Units', 'normal', 'Position', [0 0 1 1]);
Then later
set(ax(1), 'Units', oldunits, 'Position', oldpos);
If you were enthusiastic enough, you could store the old units and position via setappdata()