Leave Project to be available only to Host Secondees

We have a requirement where the Leave Project e.g. XYZ - Leave project, should be visible only to the Assignment Category - Host-Secondee employees (a secondee is a type of expatriate, and services are rendered to a host company outside of his current location) and not to any other type of Employees.

At present all are able to enter the Leave while selecting the Leave Project in the Time Card however the leaves for all other employees (other than Secondee) are integrated from Absence Management.

So the requirement is that the Leave Project in the Time Card should be visible only to the Secondees and not any other category of employees - how can we make this possible as the Time Layout Set is common for all?