If you call SUN they will tell you to wait 02 business days before taking the part III exam.
But this is not a requirement... most people that have passed both phases (2 and 3) have taken the exam even in the same day they have uploaded the project.
Besides the fact that you don't get any kind of confirmation that I saw - I just kept an eye on the Cert site after upload to see when they were done grading it.
But there's no requirement to wait.
Theodore Casser
Code Poet
Maybe he went home and went to bed. And took this tiny ad with him: