>>>>Do you use inputmask, e.g. "99:99" and format "R"?
>>>
>>>We have InputMask as below and no Format.
>>>

>>>!!:!! !!
>>>

>>
>>First of all, use "R" format. It will improve this thing, i.e. you will not get :: anymore. You could also make further improvements, e.g. by moving AM/PM part to separate box, or by resetting it in InteractiveChange event.
>
>What is your thought about using the InteractiveChange event to handle the AM/PM?

You know, after thinking a bit, I would not even use InteractiveChange. You could instead use KeyPress event, something like this:

LPARAMETERS nKeyCode, nShiftAltCtrl
IF this.SelStart=6
	IF INLIST(nKeyCode,65,80)
		RETURN
	endif
	nodefault
endif

Also, use Inputmask '99:99 !M'.