Java Security

Is it posible to modify the JVM's security policy so that applications that run on webstart(which runs on the JVM) will not present the warning(i.e. "This application has requested read/write access to a file on the local filesystem. Allowing this action will only give the application access to the file(s) selected in the following file dialog box. Do you want to allow this action?") when a non sandbox type command is executed? I tried modifying the global security file giving any codebase all permissions, but I still get the pop up window message. Is the message unavoidable?
I am writing an application to be used by a client after he runs a cript locally to change his permissions. I don't want the popup to ever appear(not even the very first time).