Disculpen, no tengo ayuda en español a mano.
The Click event occurs when the user:
Clicks a check box, command button, combo box, list box, or option button with the left mouse button.
Presses the SPACEBAR when a command button, option button, or check box has the focus.
Presses ENTER when a form has a command button with its Default property set to True (.T.).
Presses the access key for a control. For example, if the caption of a command button is "\<Go", pressing ALT+G triggers the Click event.
Clicks the text entry area of a spinner.
The Click event also occurs as a result of code you include that issues the MOUSE command.
También pueden manejar el enter desde el método keypress del formulario con keypreview en .t.
El metodo valid en otros controles se dispara entre el enter y antes del lostfocus. Si valid retorna 0 o .F. no llega a lostfocus y el foco queda en el control.
Saludos: Miguel