DFL TextBox, how to prevent key presses handled by default handler ?

[Sai]

In DFL textBox, I have a handler to get key-press events

textBox.keyPress ~= &onCmdKeyPress;

Where onCmdKeyPress is my key handler:

void onCmdKeyPresss(Object obj, KeyEventArgs kea)
{
  // my code
 kea.handled = true;
}

Irrespective of what I do with kea.handled, the key pressed is
always appearing in the text box, how can I prevent it ?

Thanks in advance
Sai