application modal dialog on OS X

I'm interested in creating a proper application modal dialog with LWM 
(modal dialog with a window title). But display dialog only seems to 
create a document modal dialog (sheet). The documentation states

If the default is not appropriate, then the programmer needs to supply 
the owner. This owner  argument can be any CAPI pane that is currently 
displayed, and the top level interface of the pane is used as the 
actual owner. The owner  can also be a screen  object, which tells the 
system on which screen to put the dialog, but none of the windows will 
be the dialog's owner.

So I tried providing :onwer as (first (capi:screens)) but this gives an 
error.

Thanks for any suggestions,

John DeSoi, Ph.D.