First of all, I would not recommend doing this.
It would be much better for you to write your own tool that will provide you with the necessary functionality.
However, if you really want to, copy all the files in C:\Windows\Microsoft.NET\Framework\v2.0.50727\ASP.NETWebAdminFiles (or Framework64 on x64) into a separate application on your website, then change Web.config and etc. to enable security. I would also recommend removing all the functions that your managers do not need, and possibly adding a log. You will also need to rewrite App_Code\WebAdminPage.cs and possibly some other files in order to work with your website.
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