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 Command1_Click()
  SelectFileListBoxItems File1, True
End Sub
 
Private Sub SelectFileListBoxItems(ctrLstBox As VB.FileListBox, bSelectAll As _
  Boolean)
 
  Const LB_SETSEL As Long = &H185&
 
  SendMessage ctrLstBox.hwnd, LB_SETSEL, bSelectAll, ByVal -1
 
End Sub