File permission for Microsoft Office fiels

I want to implement file server in my organisation in which we are using win server 2008 r2 and office 2007 

i want settings like given below :

Head of dept can create and delete the folder as well as files.

users in that dept can modify the ms office files butcan not create and delete files in any folder or sub-folder on server.

only particular group members should have limited access to resp folder and subfolders.