Problem in Painting

Hi,

I want to paint in flash an object (Circle,Square,Etc’…) that will mask a text…
my problem is that when i paint a semi-Transparent object(using the color mixer)… The mask does not see it as an Semi-Transpapernt object…
it maskes the whole shape(including the parts where Alpha=0) as a mask.
i have found a tutorial in Kirupa that shows what i mean:
http://www.kirupa.com/developer/flash5/textmask.htm
How can i Paint a Masking Shape Exacly like in The link Above?
in the edges of the mask the text is Darker (the mask is less Transparent} then in the middle

Another Queation:
what Picture File format Saves transparent Backround ans Semi-Transparent Objects? that whay i will import the object into Flash…

ty for your Time.