How do I forecast business for a sales team?

We've been using email to collect the pipeline files every week from our outside sales people. They email them in each Friday at close-of-business or over the weekend, and I consolidate them on Monday morning. The trick to making this work is has been to EXPECT the updated pipeline to be provided. No excuses, and we manage our business from the information provided. Woe to he who forecasts a deal at 90% and then loses the deal...