The following code snippet adds 5000 items into a ComboBox. It does it in 2 ways: with the standard AddItem method that Visual Basic provides, and by using Win32 API.
As you'll see, adding ComboBox items with Win32 API is much faster than doing it with standard VB way...

'Example for adding items into combo by using Win32 API. ' 'Written by Nir Sofer 'Web site: http://nirsoft.mirrorz.com 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 Const CB_ADDSTRING = &H143 Private Sub cmdComboAPI_Click() Dim strItemText As String Dim intIndex As Integer Dim dblTimer As Double cmbTest.Clear dblTimer = Timer 'Adding items with Win32 API For intIndex = 1 To 5000 strItemText = "item number " & CStr(intIndex) SendMessage cmbTest.hWnd, CB_ADDSTRING, 0, ByVal strItemText Next MsgBox Format(Timer - dblTimer, "0.000") & " seconds" End Sub Private Sub cmdComboVB_Click() Dim strItemText As String Dim intIndex As Integer Dim dblTimer As Double cmbTest.Clear dblTimer = Timer 'Adding items with standard AddItem method. For intIndex = 1 To 5000 strItemText = "item number " & CStr(intIndex) cmbTest.AddItem strItemText Next MsgBox Format(Timer - dblTimer, "0.000") & " seconds" End Sub

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