Hai ragione..una svista, prova questo:

codice:
Private Sub Command1_Click()
Dim matrice() As Integer, I As Integer
I = -1
For n = 0 To List1.ListCount - 1
    If List1.Selected(n) Then
        I = I + 1
        ReDim Preserve matrice(I)
        matrice(I) = n
    End If
Next n
For n = 0 To UBound(matrice)
    List2.AddItem List1.List(matrice(n))
Next n
For n = 0 To UBound(matrice)
    List1.RemoveItem matrice(n)
Next n
End Sub

Private Sub Command2_Click()
List2.Clear
For n = 0 To List2.ListCount - 1
    List1.AddItem List2.List(n)
Next n
End Sub
fammi sapere..ciao