>For example, 2 applications - 1 user license,
>User A use his password login PC1 (1st application)
>User A user his password login PC2(2nd application)
>So, User B can use UserA login and run the 2nd application in PC2.
>
>I want to prevent it

Then you store the triplets - app, user, workstation (you can get the latter two from sys(0) function), and keep count of user+workstation pairs only. That'd also prevent the same user running two apps on two machines.