Is there more than one file on the client that can be picked up with the *.txt? Your "TO" UNC does not list a share name after the server. Only guessing here. Use the @error and @Serror macros to determine the actual error encountered so that you can make the proper corrections.
COPY ("C:\LOCALDIR\Subfolder\*.TXT" "\\SERVER\DIR\@WKSTA.TXT")
? "Copy: @error @serror"
