Grabbing a value from a combination container

SharonH

I have the following in my DCT:
<symbol-table>
<symbol name="IMAGE">
<container combination="and" hide-name="f" name="IMAGE">
<itemref name="{iw_attributes}"/></container>
</symbol>
<symbol regex="^(.*/)?IMAGE/{iw_attributes}$">
<container combination="and" hide-name="t"
name="{iw_attributes}">
<item name="SOURCE">
<browser size="60" extns=".gif,.jpg,.jpeg" initial-dir="/images"/>
</item>

But I can't seem to output the SOURCE value in the presentation template. I have tried all the obvious combinations to get this value but none of them can pick it up - any suggestions?