Just call mkdir C:\VTS
no matter what. It will simply report that the subdirectory already exists.
Edit: As others have noted, this does set the %ERRORLEVEL% if the folder already exists. If your batch (or any processes calling it) doesn't care about the error level, this method works nicely. Since the question made no mention of avoiding the error level, this answer is perfectly valid. It fulfills the needs of creating the folder if it doesn't exist, and it doesn't overwrite the contents of an existing folder. Otherwise follow Martin Schapendonk's answer.