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Synchronise the scrolling of two listboxes

Synchronise the scrolling of two listboxes

To synchronise the scrolling of two listboxes use the following routines:

Option Explicit
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

'Purpose     :  Synchronises the scrolling of two listboxes
'Inputs      :  lhwndMasterListbox              The handle to the listbox with the focus.
'               lhwndSlaveListbox               The handle to the listbox which is to
'                                               follow the scrolling of the master listbox.
'Outputs     :  On successful returns zero


Function ListboxSynchronise(lhwndMasterListbox As Long, lhwndSlaveListbox As Long) As Long
    Const LB_GETTOPINDEX = &H18E, LB_SETTOPINDEX = &H197
    
    ListboxSynchronise = SendMessage(lhwndSlaveListbox, LB_SETTOPINDEX, SendMessage(lhwndMasterListbox, LB_GETTOPINDEX, 0&, 0&), 0&)
End Function

'Demonstration routines.
'Place inside a form containing two listboxes.
Private Sub List1_Scroll()
    ListboxSynchronise Me.List1.hwnd, Me.List2.hwnd
End Sub

Private Sub List2_Scroll()
    ListboxSynchronise Me.List2.hwnd, Me.List1.hwnd
End Sub


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