Private Sub Worksheet_Change(ByVal Target As Excel.Range)
 
    If Not Intersect(Target, Range("I1:I500")) Is Nothing Then
        If IsNumeric(Target.Value) Then
            Application.EnableEvents = False
            Target.Offset(0, 1).Value = Target.Offset(0, 1).Value + Target.Value
            Application.EnableEvents = True
        End If
    End If
End Sub

Sub Заменятель() 
For Each cell In Selection 
cell.Formula = cell.Value 
Next cell 
MsgBox "Я всё сделал!" 
End Sub