[flexcoders] not kosher to call function from inline renderer?

[Paul Hastings]

don't know if it's not kosher or i'm flubbing something but i keep getting
"Call to a possibly undefined method blobToImage." errors from something like 
this (trying to convert bunch of BLOBed thumbnails into a list):

<mx:HorizontalList id="sampleImageThumbnails" 
dataProvider="{sampleData.sampleImagery}" width="100%">
<mx:itemRenderer>
<mx:Component>
<mx:Image height="{data.data.imageHeight}" width="{data.data.imageWidth}" 
source="{blobToImage(data.thumbnail,data.imageHeight,data.imageWidth)}" />
</mx:Component>
</mx:itemRenderer>
</mx:HorizontalList>

the method is there & works (more or less ;-).

any ideas?

thanks.