Option Explicit
 
Sub Tst()
Dim Fichier As Variant
    ChDrive ThisWorkbook.Path
    ChDir ThisWorkbook.Path
    If IsEmpty(ShDatas.UsedRange) Then
        MsgBox "Feuille Vide : Rien à enregistrer", vbOKOnly + vbInformation, "Info"
        Exit Sub
    End If
    Fichier = Application.GetSaveAsFilename(InitialFileName:="Essai", fileFilter:="Fichier Txt (*.txt), *.txt" )
    If Fichier <> False Then Ecrire Fichier
End Sub
 
Private Sub Ecrire(ByVal NomFichier As String)
Dim Chaine As String
Dim r As Long, c As Integer
Dim NumFichier As Integer
Dim FirstRow As Long, FirstCol As Integer
Dim LastRow As Long, LastCol As Integer
 
    With ShDatas
        FirstRow = .Cells.Find("*", .Cells(.Cells.Count), xlFormulas, xlWhole, xlByRows, xlNext).Row
        LastRow = .Cells.Find("*", .Cells(.Cells.Count), xlFormulas, xlWhole, xlByRows, xlPrevious).Row
        FirstCol = .Cells.Find("*", .Cells(.Cells.Count), xlFormulas, xlWhole, xlByColumns, xlNext).Column
        LastCol = .Cells.Find("*", .Cells(.Cells.Count), xlFormulas, xlWhole, xlByColumns, xlPrevious).Column
    End With
     
    Close
    NumFichier = FreeFile
 
    Open NomFichier For Output As #NumFichier
        For r = FirstRow To LastRow
            Chaine = ""
            For c = FirstCol To LastCol
                Chaine = Chaine & Cells(r, c) & String(20 - Len(Cells(r, c)), " " )
            Next c
            Print #NumFichier, Chaine
        Next r
    Close #NumFichier
End Sub