You need to create a page that opens a portlet. Put in the portlet one script block that opens the new window.
Script block takes the url from a control:
var linkId = CAF.model("#{activePageBean.clientIds['htmlOutputLink']}");
leftVal = 0;
topVal = 0;
newWin = open(linkId.getValue(),"wexWindow",'width=1136,height=868,left='+leftVal+',top='+topVal+',scrollbars=no,menubar=nolocation=no,toolbar=no');
Hope this help.
Regards
#MWS-CAF-Task-Engine#webMethods#webMethods-BPMS