Class FormulaList(Of T)
        Inherits List(Of iValue(Of T))             '<<<---<<<---???
 
        Shadows Sub Add(_item As iValue(Of T))
 
            If TypeOf _item Is iFormula(Of T) Then             '<<<---<<<---???
 
                Dim tFormula As iFormula(Of T) = DirectCast(_item, iFormula(Of _
                  T))
                '<<<---<<<---??
                tFormula.Calc()
 
            End If
        End Sub
    End Class