Peter,
I would like to see all picklists in Sesame work the way you describe. But until that happens, here is an example of what Mark has suggested.
var vList as String
vList = @XListValues(@Fn, "MyForm!MyComboBoxLE")
vList = @SortStringArray(vList, 0) //0 = ASCII sort, 1 = Number sort
vList = @UniqueStringArray(vList) //Removes duplicates
PopulateListElement(MyComboboxLE, vList)
MyComboboxLE is, of course, a ComboBox type of layout element. This means you would need to change "camper:" in your example, to a ComboBox.
var vList as String
vList = @XListValues(@Fn, "cw06!!camper:")
vList = @SortStringArray(vList, 0) //0 = ASCII sort, 1 = Number sort
vList = @UniqueStringArray(vList) //Removes duplicates
PopulateListElement(camper:, vList)
Optionally, you could also build a list of selections that fit a certain criteria that is in another LE, by replacing @XListValues with @XLookupAll. This way, your list would only contain a list of campers from records where the external key LE was the same as in the key LE in the current form. Like the following:
vList = @XLookupAll(@Fn, MyKeyLE, "MyForm!MyKeyLE", "MyComboBoxLE")