Here's an old MSDOS technique to blank an open file which still works with W2K. Never tried this technique with Progress, so back up first! (Or you could install unix). By the way, the blank "echo" command mentioned above is an enquiry as to the current state of MSDOS "command echo" rather than a unix-like "echo".
copy /Y nul: myfile
The MSDOS device "nul:" is equivalent to unix "/dev/null".
The "Y" overrides the "Overwrite?" check.