The CountParam property retrieves the count of the OLE event's arguments. Use the Param property to retrieve an OleEventParam object given either the index of the parameter, or its name.

The following VB sample shows how to enumerate the arguments of an OLE event:

Private Sub ExplorerTree1_ItemOleEvent(ByVal Group As EXPLORERTREELibCtl.IGroup, ByVal Item As EXPLORERTREELibCtl.HITEM, ByVal Ev As EXPLORERTREELibCtl.IOleEvent)
    On Error Resume Next
    Debug.Print "Event name:" & Ev.Name
   If (Ev.CountParam = 0) Then
      Debug.Print "The event has no arguments."
   Else
      Debug.Print "The event has the following arguments:"
      Dim i As Long
      For i = 0 To Ev.CountParam - 1
         Debug.Print Ev(i).Name; " = " & Ev(i).Value
      Next
   End If
End Sub