trying to make a hyperlink with an id to open in a new window

Hi,

I have made a report where there are created hyperlinks to an internal website. The problem is that those links open in the same window, and I want to have them opened in an new window. I'm using this hyperlink ="http://server/iProject/Consultancy/projectdetail.aspx?id="&Fields!projectnumber.Value. I'm reading everywhere to use  Target"_blank" or rc:Linktarget=_blank, but I'm not succeeding in combining this with my link. Can anyone help me?

="javascript:void(window.open('"&"http://server/iProject/Consultancy/projectdetail.aspx?id="&Fields!projectnummer.Value&"','_blank')"