I'm not positive, but I think the entire 9 nights will be credited only after you check out, and the silver status automatically granted upon it. So your status is never technically silver in Accor system during the stay.

From what I see the only differences to your stay experience being silver vs blue are the welcome drink coupon and 2 pm late check out. If you really want these, I see two things you can do:

1. Break the stay: first stay x days that will make your 10th night with Accor, check out and move to another (possibly also Accor) hotel and check back in with the first hotel (if so desired) in 2 days (stay credits can take from several hours to more than a day to post most of the time).

2. Easier way, just have a pleasant talk with the reception, explaining that you'll hit your 10th night sometime during the 9-night stay and politely asking whether it would be possible for them to give you the welcome drink sometime during the stay and the 2 pm check out (if needed) on your last day. Hotels are in hospitality business and most would happily grant reasonable requests to earn the good faith of their customers.