Calculate time diff in yyyy-mm-dd-hh:mm format

how do u find difference between 2 times in yyyy.mm.dd hh:mm format in excel 07, i've spent hrs trying to reformat the cells, tried every concoction and all i keep getting is #VALUE!


col A
2010-12-27-06:27
2010-12-27-08:45
2010-12-27-09:37
2010-12-27-10:33



col B
2010-12-27-08:10
2010-12-27-09:15
2010-12-27-10:29
2010-12-27-13:38


and i'm trying to subtract A from B but getting nowhere, i'm trying to get the answer in dd-hh:mm
i'm looking for the time elapsed.


thanks for any help anyone can give