Option Explicit
Private Sub Workbook_Open()
Dim t() As Variant, i As Long
With Feuil2
ReDim t(1 To .Range("A65536").End(xlUp).Row)
t = Application.Transpose(.Range("A1", .Range("A65536").End(xlUp)))
ReDim Preserve t(1 To .Range("A65536").End(xlUp).Row + .Range("B65536").End(xlUp).Row)
For i = 1 To .Range("B65536").End(xlUp).Row
t(i + .Range("A65536").End(xlUp).Row) = .Cells(i, 2)
Next i
End With
Feuil1.ComboBox1.List = t
End Sub