It seems to me that you can view your camera's on your laptop localy in the shop because you are on the shop (local) network, to view the camera's away from the shop network your going to need a static i.p address at the store, then make sure all the correct ports have been forwaded on your router to allow access (see dvr set-up for correct ports) , you should then be able to log into your dvr using the static i.p address and the user name and password.
Regards
Iain