Need a override for already existing List validation

[appunu]

Hi guys,
I have a worksheet which contains a macro which will select the elements from the list validation and seperate them with a comma and display them in the same list box. There is also a "." which will actually empty the List box. This functionality works fine. Here i need some kind of override , wherein i can set elements in the entire Data validation List column to be forced to someelement,somelement1 by having an extra List Validation which contains all the combination of the elements present in the List.

Eg:- I have attached a sheet . In that there is a column named Browser. Which is a List and it contains 4 items. When we select one item it will be displayed on the List and when we select the other item the previous item is being appended with the new one with a comma seperator. When we select the Period, the List empties. Now i need some override at the top of the Browsers coulmn, which will be empty at the beginning which means no override. It will also contains elements like *firefox and safari , firefox and ie, firefox , ie , safari , ie and safari. When the override listbox is set the entire browser column changes to the forced elements.

Like if we select firefox and safari in the override element, the Actual List box should display *firfox,*safari.

Thanks in advance.

[appunu]

can anyone help me with this problem?