Above 24 Hrs time difference

This is my first post so forgive me for any mistake.I have created formula below to calculate the time difference which is above 24 Hrs.It works to some extend but not accurate.So please help me out (I cant use the date/time format in my worksheet).Any VBA code to solve this is also welcome(I have attach a sample for this).I am using excel 2003/2007 both.
Thanks

=IF(B1<=D1,IF(C1<=A1,IF(D1<B1,D1+1,D1)-B1,IF(D1<B1,D1+1,D1)-B1+DATEDIF(A1,C1,"d")*1),IF(IF(D1<B1,D1+1,D1)-B1<="24:00",IF(D1<B1,D1+1,D1)-B1,IF(C1<=A1,IF(D1<B1,D1+1,D1)-B1,IF(D1<B1,D1+1,D1)-B1+DATEDIF(A1,C1,"d")*1)))