code popup using hyperlink control?

I'm trying to code a pop-up box using the hyperlink control because I want to control the visibility of this control from my .cs file, I have a working code using the standard HTML link control however when I tried using the hyperlink control, it doesn't work at all.
<asp:HyperLink ID="newEnrollmentLink" runat="server" NavigateUrl="javascript:window.open('/mywebsite/page.aspx?id={<%# Eval(enumCP.NewId.ToString().Trim())%>}&etn=mytable','Popup','toolbar=no,location=no,directories=no,status=no,menubar=no,resizable=yes')"><u>New</u></asp:HyperLink>
Any help is appreciated, somehow my page reads the "Eval" line as pure text and doesnt pass the 'NewId' gotten from my enum into it. Advice needed, thanks!

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