Letter Of Offer - Adding A Clause On Annual Leave

Hi Memebers
we would like to add in a clause in the offer letter pertaining annual leave.
We would like to advise staff to go on annual leave while the country that they are serving is on public holiday.
Can I pharse it as per follow:
You shall go on annual leave as and when advised by your superior if the country that you are serving is on public holiday.
Appreciate your advise.
Thank you.

Public Holiday is different.
Annual Leave with wages is different.
Why you are clubbing both I don't understand. It is not correct.

Hi D. Gurumurthy
We are actually a shared service division. Staff are based in Malaysia and provide services to the Australia stakeholders.
Thus, we would like to advise staff to go on annual leave while Australia is on public holiday. Else, staff will be very free in the office.
Would appreciate your advise.
Thank you.