You cannot.
This is a browser security feature.
Would you want some rogue web site opening documents (that may or may not be
infected) on your computer without your permission?
The only way would probably be if you had an embedded ActiveX control and
the user accepted its security warning.
I understand the security issue, but it seems I've seen sites where a downloaded document is opened in a new window...or is this is
old style, eliminated as security over time has been upgraded ?
You can specify that you want a document opened in a new window or the same
window, but the user must still accept the opening of the file via a dialog
box. This security feature has been in place for many years; ever since I
can remember.
--
I hope this helps,
Steve C. Orr,
MCSD, MVP, CSM, ASPInsider http://SteveOrr.net