Fields delimiter: show "no_image.jpg" when noimage

Hello,

I want to show in a list, users snapshots (webcam captures).
I did a "field delimiter" to show it:

<img src=" chatin.tv/components/com_videowhisperlivestreaming/snapshots/ [username]_thumb.jpg" border="0" alt="No Image" style="border: 0px solid; width: 148px; height: 100px;" />

And it works. But, of course, when the image doesnt exist, the field shows a blank space with the text "No Image".

I would like, when "No Image", field delimiter shows "no_image.jpg".
How could I do it?

As it's an external URL there's no way to add a substitution IF statement to verify it; would need to be done with PHP to verify the URL response. Best bet is to probably add a background to the img tag using CSS and it should show if there's no image.