This particular function is not available in the application object function library. So program is unable to identify the function and there is an error message. Can you mention which version of STAAD.Pro you are using?
You can check the available OpenSTAAD functions in the following document --
Help > Contents > OpenSTAAD Documentation > OpenSTAAD Functions
Also you can mention about your requirement (what value you want to extract using this function) so that I can help you to find an equivalent function for this.
You can check the available OpenSTAAD functions in the following document --
Help > Contents > OpenSTAAD Documentation > OpenSTAAD Functions
Also you can mention about your requirement (what value you want to extract using this function) so that I can help you to find an equivalent function for this.