Hi Sundeep,
You may call WINDOW.CONFIRM function as in below links.
http://scn.sap.com/thread/28894
http://scn.sap.com/thread/114155
http://scn.sap.com/thread/1694976 ( I guess you have to read the code as
'var ok = WINDOW.confirm ..' )
Or
Call a new page 'VENDORPOPUP.HTM' as in below link.
http://scn.sap.com/message/1286472
Regards,
Nisha Vengal.