# Excel formula to get time difference as a decimal number

microsoft excelmicrosoft-excel-2010worksheet-function

I have a table like this (the C column is blank):

A          B           C

1  19:30      23:00       (3.50)

2  14:15      18:30       (4.25)

I need to calculate the time difference in each row between column A and column B (always BA), and put it in column C as a decimal number (as shown inside the parentheses).

Which formula should I use? Is it possible to generate a general formula, so I won't have to change the row number every time (maybe INDIRECT)?