How to restrict accessing my web application in public PC (Browseing Center) ?? // Or Allow only certain IP to Access my web application ?? Any Idea ??

Hi to all ....
This question may be weird to every1 ... But , i need to do this .... Plz help me ... ???
I have developed An Inventory Management System in ASP.Net .
The application is hosted now ... From manager to data entry operator every1 z having seperate login , roles and limitation to access website ... From Our office every1 is accessing the application and working on it .
My question is even they can access the apllication from public PC (Browseing Center) ?? coz they knew the password ... Am i rite .... !!!