If you want max(year) or any other year selected in that field to stay selected even if you press selcted then go by Andews's way but if you want that when you press clear year should be cleared also. Then, go by triggers way as Thilo suggested.
One thing to note here is that if you go by Always one selected value as suggested by Andrew then you will never be able to select more than one year. (for example you can not select 2010 and 2011 both).
So, it all depends your requirement but always one selected mode should be preferred over triggers.
Thanks for your detailed explination. See what i am thinking is i can not use "onOpen" trigger, because 1st timelogin that is fine with trigger, but if I am playing on different tabs and comeback to dashboard , then the trigger will reset my year selection to max(year) insted of keeping my selection from different tab. I did not know how Andrew option works because "Always one selected value" is disable for this list box in my case.
See all i need this selection only 1st time login. So i am thinking of set this when login only. so after login and play with different sheets and still maintain the year selection across the sheets.
Is there any way i can incorporate this trigger or some thing during the authientacation.
Always one selcted is not disabled for your liast box. You first select any one value then go to list box properties and then it will be available.
Also, for your requirement on open trigger should work fine because it is not dependent on tabs, so if you go to different tab, do some selections and come back to first tab it will not change your selections. This behavior is of on Activate sheet trigger.
On Open trigger will work when the application is opened by the user. So, a user opens an application then this trigger will run and select max(year) in your year field but then it will not run for his entire session. Then again user closes the application and next time it again opnes then it will again run the trigger.