I have 2 cells with Date and time each

Cell A1 :2/11/2014 12:05:00 PM . I need to subtract the time from 6 PM same day. which gives me 5 hours 55 minutes.

The formula I have used is

=IF(TEXT(A1, "hh:mm")>"18:00",0,TEXT((DATE(YEAR(A1),MONTH(A1),DAY(A1))+"18:00")-A1,"hh:mm"))

Cell A2 : 2/14/2014 5:05:00 PM

For the second time i calculate the time taken from 9:30 in the morning which is

=IF(DATE(DAY(B1),MONTH(A1),YEAR(A1))=DATE(DAY(H10),MONTH(H10),YEAR(H10)),0,TEXT(B1-(DATE(YEAR(B1),MONTH(B1),DAY(B1))+"9:30"),"hh:mm"))


I face a problem when i try to sum the differences i.e the sum of the differences

Can anyone help in adding the results of these formulas