ActiveX - How To Save Excel Workbook To Network

I have an ActiveX Javascript function, that pulls data from an HTML table and then populates an Excel Workbook. This works OK, but I need to save the workbook to a network path. I have successfully saved it locally:

Code:
// Save the Excel Workbook
xlBook.SaveAs("C:\TEST.XLSX");
But this does not:

Code:
// Save the Excel Workbook
xlBook.SaveAs("\Server\Projects\TEST.XLSX");

When attempting this, I get this error:
SaveAs method of Workbook class failed
Which refers to the above. I have tried different variations, but with little success (sometimes the path will default to the Server's 'My Documents'/'User Shared' folder, with the filename:
ServerProjectsTEST.XLSX