Disabling (or capturing) CTRL+A in SyntaxEditor

Hey,

I wish to supply a different implementation for the SelectAll Command and I thought to implement it by capturing the CTRL+A key event (up or down).

I was unsuccessful even after unbinding the SelectAll command using:

foreach (KeyBinding item in editor.InputBindings)
{
    if ((item.Key == Key.A) && (item.Modifiers == ModifierKeys.Control))
    {
        editor.InputBindings.Remove(item);
        break;
    }
}

How can i achieve the desired effect?

Thanks,
Tal