Although Acrobat doesn't have a link code that will force a Weblink to open in a new window, here's how you can make it happen :
Rather than linking directly to the URL you want to open, create a link to an HTML document that contains no text. The HTML document immediately opens a new window itself, using HTML code rather than Acrobat's syntax, and opens the desired URL in that window.
The Acrobat Weblink will be a normal link to an HTML page that has nothing in its body and includes the following line in its head:
< META HTTP-EQUIV="Refresh" CONTENT="x; URL=zzz" >For x, substitute the number of seconds that should elapse before the new link opens (in this case, probably zero), and for zzz, substitute the URL that should open in the new window.
I have a similar problem when generating pdf's with /URI hyperlinks for use in Acrobat Reader 9 and 10 displaying the pdf in IE.
When the hyperlink is clicked, I want a new IE window to open up to the given url. (This will display reference information for help in filling out the form.)