Create a script to find the Excel file path link in your web application and store it in your local system.
There should be some way to find/identify the link path. I can mention the code and object repository entry details if If see your web application.
And then, you can access the saved Excel using createobject as below.
Set objExcel = CreateObject("Excel.Application")
Using this objExcel, you will be able to do whatever (including renaming file) you can do with Excel manually.
You can refer this article
for sample usage of this excel object.