How can I call popup's using XML

[Seppel2k]

I'm using the following XML Table for my drop down menu in flash:
<NAV main_onColor="#FF9933" main_offColor="#FFFFFF" sub_onColor="#FF9933" sub_offColor="#FFFFFF" navWidth="640" x_padding="40" y_padding="10">
<MAIN text="PzGrenBtl 421 - 2oo4">
<SUB text="Kp Gebaeude" URL="" target="mainFrame"></SUB>
</MAIN>
</NAV>

There are certainly more then just one entry...the thing is, I can write in the URL space URL="

http://www.xyz.de"

But how can I call up this page as a popup...?

Thanxs Seppel