I am currently using Excel 2007

In Cell A1 I have a start date of 14/6/13 09:01
In cell B1 I have an end date of 19/6/13 14:37
I have the following formula to calculate Hours and minutes
=INT(B1-A1)&TEXT(B1-A1,":hh:mm")

In Cell C1 i have another start date of 19/6/13 15:00
In cell D1 I have another end date of 20/6/13 17:32
I have another formula as above to calculate the hours and minutes

Is there an easier formula?

I would like to add the two calculated dates so I have one total.
I would also like it to calculate days, hours and minutes based on working days of Monday to Friday 9am to 5pm.