>the new control When event occurs before the lostfocus of the old control, thus you can (for example)_set some property that will tell the lostfocus event to skip validation if the new control is such a button

This order of events only holds true for clicking, not for tabbing. When tabbing from control to control the lostfocus of the first control fires before the when of the second. For the particular case being asked though- oyur solution might solve the problem...