Multi regions mask

Hi,

i would like to have a particular preloader and for that i was thinking to have a multi region mask.

basically i have 5 squares spaced by 10 pixels and i would like to make my bar scrolling behind those 5 squares.

therefore those 5 squares should be the mask.

however, when i use those 5 squares like a single movieclip, my scrolling bar is visible among squares… it’s like everything from my movieclip is taken as mask (and not only squares).

how can i tell to flash cs3, that only those 5 regions (5 squares) are the mask (and not space between 2 squares) ?

thanks a lot,

A