Checking for existence of file

[Brudderman]

I have a web viewer configured to view bitmap scans of purchase tickets. Since the bitmap files are named based on the ID field, the file path to the saved file (e.g., c:scans00019.bmp) is easy to calculate. With a script activated with the View button, then, I open a pop-up window with a web viewer for viewing the file. This works

well, but if a particular ticket hasn't been scanned, there's no file at the computed path and the web viewer displays an error page.

How can I check for the existence of the file before displaying the web viewer? Alternatively, can I trap a web viewer error for a bad URL?

As an added feature, it would be nice to have the View button be visible only when a valid path exists.

I'd appreciate any thoughts on how to do this.

Thanks!