RemoveFile: I use the RemoveFile command to delete a temporary file before creating a new one. Since the file doesn't always exists, I'm getting a syntax error message in the GuiXT script window. Is there a way to avoid this message?
You can omit the RemoveFile statement in your script, since

OpenFile ... -output

deletes the file content before writing new data to the file.

If you really need a way to determine whether the file exists, without getting an error message in the script window, use

CopyText fromFile= "..." toText= "x"

if Q[ok]

...

endif