Annoying sound in TextBox when pressing ENTER

Hi everybody,

I'd like to ask for a little help regarding some annoying sound when I
press ENTER on TextBox. My device running WinCE 4.2 gives the sound
like "illegal key", however the ENTER is handled. This sound is
independent of TextBox.AcceptReturn. I've tried handling e.Cancel in
KeyPress, KeyUp and KeyDown, I've tried even creating custom class
deriving from TextBox and overriding KeyPress, KeyUp and KeyDown
events, but with no success. The sound remained. Could anyone point me
some solution?

Thanks in advance, e@7.