APEX

Hi,
On my one of the pages of my site, i have list of some items and every item value is a link and if i click the item name, a pop up appears which shows me history of the item. On this history item pop up, i have two date picker elements where i provide the begin and end date between which i want to see the history of this item. I have add two computations (before header) to set the values of date pickers to the minimum date and maximum date by querying history dates for that item from the database and on first time, it shows complete history of the item in the pop up. Now, i can select my own minimum and maximum dates from the date bicker element and press a button, now the pop up refreshes and shows me the history between the dates i have selected.
Now, i close the pop up windows and click on some other item, but here when pop up is loaded, i see the old values of date (which i selected for previous item) in the date picker and ideally my computations should have worked and date pickers should have seen the minimum and maximum dates for this item.

Can any one help me to resolve the problem so that when ever a new pop up is opened for a new item, the date picker element should have refreshed values in them which should be related to the new item on which i clicked right now rather than date values of previous item.

Thanks in advance

Salman