Hiding CSS in BI launchpad

Is there a possibility to hide the css-file of an application from the end-users in bi launchpad so that it still works in the dashboard?
It is possible with all documents in the bi launchpad (i.e. webi, crystal, design studio application,...). But when I hide the root folder from the css-file and get view-access to the folder that holds the css-file, I don't get css-styles in my dashboard.