The easiest way would be to use XCOPY in combination with the /D parameter. This will only copy changed files (determined by the last-modified date stamp). Check all available XCOPY parameters with XCOPY /? at the command prompt.

However, if you do not remove the saved files on the client computer, then all users will have access to all saved files for all users. I don't think you want that? If you do, then what's the point of copying the saved files to the user's network staorage?
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There are two types of vessels, submarines and targets.