The limit on a filename is 255 and the limit of path+filename is 260. If you are seeing 280 in length this means your share path name (\\Server01\Username) is smaller than the path where the files are actually store on the server (D:\Data\Users\Username\). This problem should also make it so you couldn't open up the long length directly from the server and you would have to open it from a share. You can increase the share length which would force them to choose shorter filenames, though if you did that without prior notification they may not be able to open files that are too long.
Another problem would come where you can increase the length of folder name containing the long filename and then you would not be able to open that file.
I am pretty sure that you cannot limit this so I would just suggest that you increase the share length in case your files can not be backed up since they went of the 260 character limit because of a possibly short share path.
As for a 3rd party utility the only thing I can think of would be something to scan your data every night and report on long file names but I don't think that is what you really want.