>want to create a temporary directory, if it does not already exist. if it does exist then i want to do nothing. what is a good method?

You can use ADIR to check if the directory exists, and verify that it is in fact a directory:

LOCAL aFiles[1,5]
IF ADIR(aFiles,'C:\TheDir\Path\ToCheck','D') = 0
   *  The directory does not exist, and there is no conflicting filename
   *  so you want to create it here
ELSE
   IF 'D' $ aFiles[1,5]
      *  The directory exists
   ELSE
      *  The directory doesn't exist, but there's a file with the same name,
      *  so you can't create a directory with this name
   ENDIF
ENDIF