How do you overwrite values in a ring control?

Hello,

I have a Ring Control (Text Values) in Labview 2009 and it is programatically populated with 20 items. The end user either selects from the items in the list or populates it with a new item based on a checkbox for adding new item. What I want to do is when the 20th item is entered and the user selects the checkbox for item 21 to be added I would like to rap around to the first item in the list and overwrite it. Is this possible and a sample vi would be great to demonstrate how this is done. Any help would be greatly appreciated!

Thanks in Advance

Charlie