public string OnClientKeyPressing { get; set; }

Public Property OnClientKeyPressing As String
	Get
	Set

public:
property String^ OnClientKeyPressing {
	String^ get ();
	void set (String^ value);
}

member OnClientKeyPressing : string with get, set

<kettic:kaxcombobox 
  Runat="server"
  ID="KaxComboBox3"       
  OnClientKeyPressing="HandleKeyPress" 
 ... 
/>

   <script type="text/javascript">

   function HandleKeyPress(sender, e)
   {
    if (e.keyCode == 13)
    {
     document.forms[0].submit();
    }
   }

   </script>