calculate number of hours between two date/time combinations

Hello,
I am trying to find a way to calculate the number of hours between date/times found in separate rows. The attached data set will help to envision what I am talking about.

For each couple of rows, I need to find a way to calculate the number of hours elapsed from row 1 to row 2. In the first example, to calculate the number of hours between 12/2/2009 8:56:51 and 12/4/2009 6:35:27.

any help is appreciated!

Thank you

Assuming the sample to be accurate (ie integer as time) and assuming time values greater than noon are entered as 130420 then

=(A3+TEXT(B3,"00\:00\:00"))-(A2+TEXT(B2,"00\:00\:00"))
format as [hh]:mm:ss

Using your example the above would result in 45:38:36 ... if you want this in decimal form (45.64333...) then multiply by 24 and format as General / Number rather than Time.