Is there a way to extract the Timevalue between two date variables?

somebody sent me the Datediff function, but that is not for what I want, I need to extract the time passed between two dateTime values, such a counter for several Internet conections in several PC's. Can you guys help me, since I am using timer controls for each PC in a Form, but if I do something else, some errors appear, such as time misvalue and others, give me a clue!
Thanks in advance!