record the data and add

Private Sub Worksheet_Change(ByVal Target As Range)
   'Do nothing if more than one cell is changed or content deleted
   If Target.Cells.Count > 1 Or IsEmpty(Target) Then Exit Sub
      
    If Target.Address = "$A$1" Then
               If IsNumeric(Target) Then
            target.copy destination:=Range("B65536").end(xlup).offset(1,0)
               End If
    End If
      
End Sub

everythijme you change the value in A1 it will be copied to a cell in column b