How to close popup window without alert box message

Hi all,
I produce a popup window by adding a hyperlink to a table cell dynamically in my vb.net code behind.  Here is the code: 
Dim sHyperlink As String = "<a href=""LabPopup.aspx?RefNo=" & iLabRefNo & """ target=""_blank"">" & strValue & "</a>" objCellValue.Controls.Add(New LiteralControl(sHyperlink)) ...