Dim oldList() As String
Dim i
 
Private Sub Command1_Click
Redim oldList(0 To List1.ListCount-1) As String
For i=0 To List1.ListCount-1
oldList(i)=List1.List(i)
Next i
List1.Clear
For i=0 To List2.ListCount-1
List1.AddItem List2.List(i)
Next i
List2.Clear
For i=0 To Ubound(oldList)
List2.AddItem oldList(i)
Next i
End Sub