GUI Access VIA LAN Address in NAT Mode

Hi, we received a lot of calls from our customers that are in NAT Mode and they can access the GUI from the LAN IP Address. Theres a way to deny GUI Access from LAN IP Address in NAT Mode ? this is a security issue that we are rally worried about. If Not we need a option to limited to access he GUI via    LAN Address in NAT Mode. But still having access via LAN with other IP ADDRESS?