Is File Writable needs to detect an open PowerPoint file as not being readable

[txnelson]

If a PowerPoint file is open, JMP can not write to that file, to either write a new file or to append  to the existing file.  However, the "Is File Writable" returns a 1 when queried, even when the PowerPoint file is open.

The "Is File Writable" function needs to recognize the open file as not being writable