How to get a xhtml page as a pop up through WebFlow? Pls help

Hi friends,

I want a xhtml file to be displayed as a pop-up.

Say the file's name is graph.xhtml

Presently I have written the flow as
<transition on="dateChange" to="showGraph">
<evaluate expression="asController.printGraph(graphBean,acco unt.accountNumber)"
result="flowScope.graphData" />
</transition>
<view-state id="showGraph" view="graph.xhtml">

And the file was displaying in a separate page.

I was suggested to add a line "popup=true" in the flow like the following line, so that this page would display as a popup without any problem.

<view-state id="showGraph" view="graph.xhtml" popup="true">

But it is not working and the page is again displaying as a separate page only. Please help me in how to bring the page as a pop-up.

Someone kindly help me