he RadUpload control offers you several events to which you can build an event handler to contain your method of changing the local file name change. Here is a list of the events:
FileTooLarge, FileCountExceeded, UploadSizeExceeded - these events can get triggered if some of the selected files exceed the predefined criteria.
FilesSelected - raises when the user has selected files from the browse dialog window. This is the first of the RadUpload specific events that can be triggered by the actions of the user.
UploadStarted - raises when the user clicks the Upload button.
FileUploadStarting - raises during the upload of each file.
FileUploadFailed, ProgressChanged, FileUploadPaused, FileUploadResumed, FileUploadCanceled - these events can be triggered in different order, depending on the user actions.
FileUploaded - raises when the file has been fully uploaded.
UploadFinished - raises when all files in the list have been processed, no matter this has been successfully done or not.
You need to just figure out when the best time would be for you to make the change in your circumstances. This link
will bring you to the documentation on the events I jsut mention.
I hope this helps, Good Luck!