Thierry,

Maybe you can use the Format Painter.  Select the cell that has the
formatting you wish to copy, and click the Format Painter.  It's a
paintbrush on a button on the Standard toolbar.  Now click the cell that's
to be formatted, and the formatting is copied.  If you double-click the
painter, you can click many cells, applying formatting.  Then turn it back
off by either clicking it again, or pressing Esc.