How to add "time" in "DateSerial" ?

- I have field that using "datetime" type (ex: 8/25/2009 10:12:16 AM)
- Now i want to make 'date beetwen' date1(start) and date2(finish). (it set by combobox month,day,year for each date)

- If im using DateSerial(combobox1,combobox2,combobox3) then the time is automatically set to "12:00:00 AM" (it mean the beginning of the day)
- Its not a problem with date1, but the problem is date2(finish)
ex: - start=25 august 2009; finish=30 august 2009;
it will make the problem 'cause finish date is "30 august 2009 12:00:00 AM" it mean 29 august 2009, right?
I want to set the time so date2 -> dateserial(30 august 2009 11:59:59 PM) (but of course its eror)

Any other way to set time? plzhlp



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