Binaryworld - ListBoxSelectRange - Select or unselect a range of elements in a ListB ... [ VB -> Forms & Controls ]

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 Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (dest As _
  Any, dest As Any, ByVal numBytes As Long)
Const LB_SELITEMRANGE = &H19B

' Select or deselect all the ListBox items in the specified range
'
' use newState = True to select, or False to deselect
' it affects all items if the last two arguments are omitted

Sub ListBoxSelectRange (lb As ListBox, ByVal newState As Boolean, _
  Optional firstItem As Long, Optional lastItem As Long = -1)
  Dim lParam As Long

  ' account for omitted lastItem argument.
  If lastItem < 0 Then lastItem = lb.ListCount - 1

  ' lParam must contain the first item's index in its low-order word
  ' and the last item's index in its high-order word.
  ' We need this method to avoid overflow.
  CopyMemory lParam, firstItem, 2
  CopyMemory ByVal VarPtr(lParam) + 2, lastItem, 2

  SendMessage lb.hwnd, LB_SELITEMRANGE, newState, ByVal lParam
End Sub