Private Sub AddHyperLink()
    Dim link As Excel.Hyperlink = _
        CType(Me.Hyperlinks.Add(Me.Range("A1"), _
        "http://www.microsoft.com", ScreenTip:="Microsoft", _
        TextToDisplay:="Microsoft's Website."), Excel.Hyperlink)
End Sub

private void AddHyperLink()
{
    Excel.Hyperlink link = (Excel.Hyperlink)this.Hyperlinks.Add(
        this.Range["A1", missing], "http://www.microsoft.com",
        missing, "Microsoft", "Microsoft's Website.");
}