Calculating time differences over different dates

Hi

Is there any way of calculating the time difference between a range of dates & times, as shown below.

I currently have the dates and times shown seperately in individual cells, into which the entries are made via a userform.

All dates are (dd-mm-yy).
All times are (hh:mm).

e.g
Scheduled
Start Date = 03-01-10 Cell Ref = A1
Start Time = 14:00 A2
End Date = 03-01-10 A3
End Time = 22:00 A4

Actual
Start Date = 03-01-10 A5
Start Time = 18:00 A6
End Date = 04-01-10 A7
End Time = 02:00 A8

Time difference between (A4-A2) and (A8-A6). Cell reference = A9 (will always be positive).

I can get it to work when I format the cells to show dates AND times but I have opted to split them as I do not know how to provide them combined via a userform.

Many thanks,

Andy