
v tomto pripade nejde pouzit vzorcu, tak pouzij makro.
ve VBA Editoru vloz do modulu konkretniho listu tento kod:
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Address = "$B$1" Then
If IsNumeric(Range("b1")) = True Then
Range("a1") = Range("a1") + Range("b1")
Else
Exit Sub
End If
End If
End Sub