How do I allow only client pc's to access web app

I have been asked to figure out how we can allow only client pc’s to access our web app such that even a legit user can not log on from home. It must be only from the office. Its just that the information is kinda sensitive and we want to avoid non screen personel from seeing them while they are being worked on.

The users have been adviced but in order to catch up with work they have been found to work while at home.

Thanks guys. I just discussed this with the boss and basically he now wants client staff restricted to some functions only when longing on from non office pc. So with what you guys have said I am thinking I will have to store the IP of the client gateway and validate the tasks requested against it.

If your application is running on Apache, you can take use of .htaccess and deny the access for everyone but allowed for the client Ips:

e.g

deny from all
allow from 11.22.33.44

Allow to connect only from work IP addresses. You can enforce that from various places:
firewall
WAF
http server configuration