Excel 2007 : List with dynamic source issue

[kentwistle]

Ok, I've got 2 named ranges: ActivityCodes (a list of activities) and PlanCodes (built by the user from the ActivityCodes, so it is essentially a subset of ActivityCodes). Now, I've got a list item where I want the source to be the PlanCodes if anything has been selected, otherwise use the ActivityCodes as the source. I have it working somewhat using this formula in the source field in the data validation area for the list:
=IF(COUNTA(PlanCodes)>0,PlanCodes,ActivityCodes).

The problem is that when I pull down the list when PlanCodes is the source, the selected item is the BOTTOM of the list, so it looks blank unless I scroll UP to see the data. Does anyone know of a way to DE-select anything from the list so that when the list is pulled down you see the list from the top?