Working time and days

I would like to be able to caculate working time when the cell format is
4/1/2005 6:40:26 AM (not seperated into date and time)

Cell A1 dd/mm/yyyy h:mm:ss (First Day)
Cell A2 dd/mm/yyyy h:mm:ss (Last day)

Working hours would be 8:00 to 17:00
Public holidays need to be taken out too

The result should be working days hours and minutes or just hours and
minutes, so that Saturday, Sunday, public holidays & between the hours of
17:00 to 8:00 to the next working day would not count.

I've tried using:

=((NETWORKDAYS(A1,C1)-2)*9)/24+TIME(17,00,0)-B1+D1-TIME(8,00,0)

But I think this will only work if the date and time are in seperate cells.

Can any one help

This was resolved in another area, thanks for the help, Steve.

"Nortos" wrote:

I would like to be able to caculate working time when the cell format is
4/1/2005 6:40:26 AM (not seperated into date and time)

Cell A1 dd/mm/yyyy h:mm:ss (First Day)
Cell A2 dd/mm/yyyy h:mm:ss (Last day)

Working hours would be 8:00 to 17:00
Public holidays need to be taken out too

The result should be working days hours and minutes or just hours and
minutes, so that Saturday, Sunday, public holidays & between the hours of
17:00 to 8:00 to the next working day would not count.

I've tried using:

=((NETWORKDAYS(A1,C1)-2)*9)/24+TIME(17,00,0)-B1+D1-TIME(8,00,0)

But I think this will only work if the date and time are in seperate cells.

Can any one help