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

 'Konstanten für die ComboBox
Private Const CB_ADDSTRING = &H143
Private Const CB_SETITEMDATA = &H151

Private Sub Command1_Click()
  Dim lngIndex      As Long
  Dim lngDataIndex  As Long

  For lngIndex = 1 To 5000
     strItemText = "Eintrag " & CStr(lngIndex)
      'Neuen Eintrag in der ComboBox hinzufügen
     lngDataIndex = SendMessage(Combo1.hWnd, CB_ADDSTRING, 0, _
        ByVal strItemText)
      'ItemData des neuen Items setzen
     SendMessage Combo1.hWnd, CB_SETITEMDATA, lngDataIndex, _
        ByVal lngIndex
  Next

  'Auf den 1. Eintrag setzen
  Combo1.ListIndex = Combo1.TopIndex
End Sub