Private Sub Worksheet_Change(ByVal Target As Range)
    If Not Application.Intersect(Range("P1"), Range(Target.Address)) Is Nothing Then
        MsgBox "Значение ячейки " & Target.Address & " изменено."
    End If
End Sub

Range("A" & bLastRow, "A" & aLastRow + bLastRow - 1).Select

Sub txt1251()
   Dim Filename As String
   Dim NumRows As Long, NumCols As Integer
   Dim r As Long, c As Integer
   Dim Data
   Dim ExpRng As Range
 
   Set ExpRng = Selection
   NumCols = ExpRng.Columns.Count
   NumRows = ExpRng.Rows.Count
   Filename = ThisWorkbook.Path & "\111.TXT"
   Open Filename For Output As #1
       For r = 1 To NumRows
           For c = 1 To NumCols
               Data = ExpRng.Cells(r, c).Value
               If IsNumeric(Data) Then Data = Val(Data)
               If IsEmpty(ExpRng.Cells(r, c)) Then Data = ""
               If c <> NumCols Then
                   Print #1, Data;
               Else
                   Print #1, Data
               End If
           Next c
       Next r
   Close #1
End Sub