How to calculate duration between 2 timestamps?

Hi,

I am using this FM CRM_ORDER_READ_OW in CRM to get the start and end time of a request.

Format - DD.MM.YY HH.MM.SS

Start time = 19.11.2012 18:09:33 CET

End time = 26.11.2012 18:09:33

Can you please guide on how can I calculate the duration in HOURS between these 2 timestamps?

Thank you very much!

Kind regards,

Rebekah