Need help to open image in a popup....

Hi all,
i'm using fckeditor 1.6 and i need to open the images that i insert or upload in a separate popup.
To get this,i found a js function on the net that can be adapted for this purpose.
It allows to set the popup title too.
This is the triggering code:
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<a href="javascript:popImage('http://SomeSite.com/SomeImage.gif','Some Title')">
<img src="http://SomeSite.com/SomeImage.gif" border="0">
</a>

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So far i've been only able to put a new button on the toolbar which opens a new dialog (called fck_popimage,cloned from fck_link).
Here comes the problem.
I have to edit this dialog so it retrieves the "src" value from the picture and then insert this value(a URL) into the "href" of the "a" tag.
Hope i was clear and someone could help me to build this useful tool.
Thanks in advance,ralf