Need help with Elapsed time using Now in VB.Net 2003

Hi,
Can anyone help with determining elapsed time?
Back when we used VB6 we had code that said something like:
StartTime = Now

Then in a different part of the code we had:
TimeNow = Now
TimeDifference = TimeNow - StartTime

Now in VB.NET 2003 I am getting errors that say: Operator '-' is not defined for types "Date'

What I really need to get is the time difference in seconds.

Any ideas?

Thanks,
Charlie