how to add on click attribute for HyperLinkField in code behind !!

hi,
i am creating a datagrid dynamically and having one column hyperlinkfield i set the following
 HyperLinkField hFld = new HyperLinkField();
hfld.navigateurl="default2.aspx";
hfld.target="_blank";
but iam not able to specify the window size and options so i thought to use the javascript window.open
how to have the below in code behid ?
<asp:HyperLink ID="HyperLink1" runat="server" onclick="javascript:w= window.open('test.aspx','mywin','left=20,top=20,width=500,height=500,toolbar=0,resizable=0');">new Window</asp:HyperLink>
but there is no attribute property to set the onclick how to solve please help?
 
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