boucle avec for avec valeur manquante

For x = TextBox1.Value To TextBox2.Value
    Dim cell_nom As Range, lg_total As Integer
    If exist_sh("Semaine N°" & x) Then
      Worksheets("Semaine N°" & x).Select
      If Worksheets("Semaine N°" & x).Range("A10") = "Nom" Then
      Set cell_nom = Worksheets("Semaine N°" & x).Columns("A").Find("Nom", , , , , xlPrevious)
      lg_total = cell_nom.Row - 2
      .....
      End If
    End If

Function exist_sh(Nom)
exist_sh = False
On Error Resume Next
  x = Sheets(Nom).Name
  If Err.Number = 0 Then exist_sh = True
On Error GoTo 0
End Function

 Dim derligbilan5 As Long
 derligbilan5 = Worksheets(feuilleBilan).Range("A" & Rows.Count).End(xlUp).Row
 'msgbox "der5 " & derligbilan5

    Rows("13:" & derligbilan5).Select
    Selection.Delete

For x = TextBox1.Value To TextBox2.Value
Dim cell_nom As Range, lg_total As Integer
    If exist_sh("Semaine N°" & x) Then
Worksheets("Semaine N°" & x).Select
If Worksheets("Semaine N°" & x).Range("A10") = "Nom" Then
Set cell_nom = Worksheets("Semaine N°" & x).Columns("A").Find("Nom", , , , , xlPrevious)
lg_total = cell_nom.Row - 2
'msgbox lg_total



'Worksheets("Semaine N°" & x).Select
Worksheets("Semaine N°" & x).Range(Cells(12, 1), Cells(lg_total, 13)).Copy
Worksheets(feuilleBilan).Select
Dim cell_nom2 As Range
Worksheets(feuilleBilan).Select

derniereLigne = Worksheets(feuilleBilan).Range("A" & Rows.Count).End(xlUp).Row 'n° de la dernière ligne non vide de la colonne A

'msgbox "derligne=" & derniereLigne

 Worksheets(feuilleBilan).Cells(derniereLigne + 1, 1).PasteSpecial Paste:=xlPasteValues
 End If
 End If
  Function exist_sh(Nom)
exist_sh = False
On Error Resume Next
  x = Sheets(Nom).Name
  If Err.Number = 0 Then exist_sh = True
On Error GoTo 0
End Function

 Next x
 

 
 
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