Option Explicit

Private Const LB_GETTOPINDEX = &H18E
Private Const LB_SETTOPINDEX = &H197
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, _
ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long

Private Sub Form_Load()
Dim i As Integer
For i =  1  To  50 
List1.AddItem "Item " & CStr(i)
List2.AddItem "Item " & CStr(i)
Next
End Sub

Private Sub List1_Scroll()
Call SendMessage(List2.hwnd, LB_SETTOPINDEX, SendMessage(List1.hwnd, _
LB_GETTOPINDEX,  0 ,  0 ),  0 )
End Sub

Private Sub List2_Scroll()
Call SendMessage(List1.hwnd, LB_SETTOPINDEX, SendMessage(List2.hwnd, _
LB_GETTOPINDEX,  0 ,  0 ),  0 )
End Sub

Private Sub List2_Click()
List1.ListIndex = List2.ListIndex
End Sub

Private Sub List1_Click()
List2.ListIndex = List1.ListIndex
End Sub