Change folder permissions

[Barand]

I want to develop an e-Tendering application where bids are placed by suppliers in "sealed" folders up to a set time on a deadline date. The site will contains invitations to tender and suppliers will download the relevant information.

 

(Currently, bids are received by post in sealed envelopes that are only opened at the prescribed date and time. I want to replicate this on the server.)

 

Currently using Win2000, IIS. PHP5

 

So, there would be a folder, say, 2007_04_30.

 

When a supplier places a bid I want to create supplierX folder inside the 2007_04_30 folder and until that date at 11am only that supplier will have read/write/delete access to documents in their folder. (I haven't decided yet whether to to it via file upload or whether use FTP, or a mix. Certain info will be collected via forms on the web pages)

 

At precisely 11am on the deadline date (bidding stops and the "envelopes are opened") I want to switch the permissions so the 2007_04_30 folder, and all the folders inside, become read-only. At the same time give read access to a new group of users (Tender Review Team)

 

So the question is - how do I change user and group permissions on these folders?