Issue while running cab file in WAP4 scanner

I am facing issue related to permission when I try to re-install my application cab file on top of existing cab file in WAP4 scanner. It is working in WAP3 scanner. How it used to work is when I try to install application on top of an existing application it used to uninstall first and than install new application. But it is not un-installing existing application and giving error 'Uninstalling is unsuccessful do you want to continue with installation" if I click OK it give error saying not able to install due to not enough permission. How to provide permission to cab file so it can run as admin ? Is there any document on how to create application cab file which run on WAP4 scanner ?