Obtaining elapsed time in decimal when time and date are in different columns - v2003

Hi,

I have a spreadsheet (attached) where I need to determine the elapsed time between when an email was received and when it was replied to. Unfortunately, the date and times come in different cells. I am subtracting the times but need to factor in whether the date also changed and need to express the result as hours with 2 decimal points. e.g.

Sent Date Sent Time Replied Date Replied Time Response Time (hrs)
17/04/2012 9:02:00 AM 17/04/2012 7:33:12 PM = Should be approx 10.5 hrs
17/04/2012 11:05:00 PM 18/04/2012 9:36:52 AM = should be approx 10.5 hrs
18/04/2012 10:05:00 AM 19/04/2012 10:13:48 AM = should be approx 24.13 hrs

Can anyone of you clever people help?

Thanks in advance

Ah! All I had to do was add the time and date before subtracting? I was trying to concatenate. Works perfectly! Thank you.