Option Explicit
Private Sub ComboBox1_MouseDown(ByVal Button As Integer, ByVal Shift As Integer, ByVal x As Single, ByVal y As Single)
Dim RefPate1 As Variant, RefPate2 As Variant
Dim TabFinal() As Integer
Dim i As Integer, ii As Integer, j As Integer
With Sheets(1)
RefPate1 = Range(.Range('E3'), .Range('E65536').End(xlUp))
RefPate2 = Range(.Range('F3'), .Range('F65536').End(xlUp))
End With
For i = 1 To UBound(RefPate1)
For ii = 1 To UBound(RefPate2)
If RefPate1(i, 1) = RefPate2(ii, 1) Then GoTo TheNext
Next ii
ReDim Preserve TabFinal(j)
TabFinal(j) = RefPate1(i, 1)
j = j + 1
TheNext:
Next i
ComboBox1.List() = TabFinal()
End Sub