Code:
open location "smb:// user : password @ computername / sharename"
tell application "Finder"
close front window
end tell
Not exactly what you were looking for, but the window doesn't remain open.
[edit] - just remembered something...
Try adding a trailing slash after the end of the URL - This may mount the drive without opening the window (maybe that's just AFP though...)
[edit2] - even better use the Mount Volume Command:
Code:
mount volume "smb://user:pass@host/share"
(you don't even need to target the Finder)