file not found

[mazzapaolo@liber]

I have a line like this:

set the fileName of image "myImage" to "image.gif"

If the file exists it works fine.
If the file does not exists, the image "myImage" gets blank, the result 
is empty, and I do not get any error-message.
How can I get a beep when Rev can not find the file?
Thank you for your help,

Paolo Mazza (Italy)