Add an image caption for Shadowbox image only?

Hi SI Team

Is it possible to add a caption for the shadow box image only?

Please click on an image here:
http://stackideas.com/blog/update-your-easyblog-acl
Note the image description which does not appaear in the blog paost!

And then go to my post here:
http://finalbug.net/blog/entry/470-youtube´s-copyright-robot-collateral-damage
And click on an image.
There is obviously no image caption text.

I can add a text using the image caption box but then I have a double caption so to speak.
The reason that I already have a caption is that I used a text block to make my caption as it offered me more formatting options!

Is there a way I can add text/caption for the shadow box only?
i.e. the way it works on the SI Blog?

thanks

Paul