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You would have to enable SMB over TM on your mac using a single command line or you can use iTimemachine which enables it for you through a GUI so you can easily disable it and enable it. Then you would have to mount the share and create a sparse bundle and put that in the TM share on the EX470. More about sparsebundles can be found here. http://www.readynas.com/?p=253

If I were you I would just make a linux box and install netatalk to enable an AFP server and create a sparsebundle for it.
 
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