The correct syntax is application.StartupPath (note the period after "application").
The reason XLStart would be empty is that you have never created the "Personal" workbook which stores macros you record or write; or you have not put any other workbook into that folder. Personal will be created the first time you record a macro and indicate that you want to store it in Personal (as opposed to the current workbook). Personal is hidden, by default.
Keep Up with TechRepublic