Sorry about the late reply, I've been in a tiny town in the middle of nowhere.
So you don't have to create the scheduled task using ASP.NET. All you need to do is create a console application. The code of the console app should simply be - call the service, get rates, call database, store rates.
You then manually create a scheduled task wherever it's going to be hosted and in the scheduled task wizard you point it to the console app EXE that you've created. Is that making sense?