hi, well if you don't want anyone to add a task or change an existing task or project you can do that by changing the resources permissions by going to Modify users and groups in the admin tab in the web access page. then choose the user you want to change his or her account and click modify, then scroll down to find the catigories you should choose catigories as you find them needed for your selected resource then go to permission and there you have to select each group and then change the permission: un check the create a new task , open project and save project. then go to global permissions and un check all the rules which have to do with the project file as a file then save.
i think this will not allow any one to edit any thing in the project except you. but the create task is useful as long as the one who create it will send you to update it in the project, he can't update it he can create it and you will accept it or reject it before uploading to the project
hope that i've helped you?
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