How to make up :popup as the top-most window?

In the main windows, 10 project names are shown. Each project name is a
link to a popup to show the project detail. Code:

<%= link_to h(project.code), project, :popup =>
['detail_window','height=560,width=900,resizable=yes'] %>

This works fine if the user closes the detail window after viewing it.

There is a problem if the user clicks another project _without_ closing
the detail window first. Since the project window is bigger than the
detail windows, the detail window is refresh but it is not the top-most
window.

It seems to the user nothing refresh when clicking different project
(the reality is the popup window is refreshed behind the project
window).

So, how can I set the popup detail windows to be top-most (even it's
opened before)?

Thanks
horace

p.s. Browser is IE 6