You do not need to use the style or the selection property to apply the borders to specific edges of the range. Just use the Item Method to specify which one you want to modify.
Method Worksheet->Range
Property Range->Borders
Method Borders->Item(xlEdgeTop)
Property Border->Weight = xlThin
Attached is you VI modified as described.
Michael Munroe
Certified LabVIEW Developer
www.abcdef.biz