QR codes into Downloads II mod

[pizzamargherita]

I've the intention to add automatically a QR for each file into the Downloads II mod I've installed into my website, to allow users downloading file from their smartphones.

I've yet found the code I need to reach this point, but it won't work properly for my case.

Check it:
The html...

<img src="http://chart.apis.google.com/chart?chs=150x150&amp;cht=qr&amp;chl=convert-this&amp;choe=UTF-8&amp;chld=L|4">

...is able to convert the text "convert-this" into a QR code.

This is the return image:


So I put the page url in place of "convert-this" to have the QR code for each download page.
I've modified the code as you can see:

<img src="http://chart.apis.google.com/chart?chs=150x150&amp;cht=qr&amp;chl=http://www.moddingstudio.com/downloads.php?do=file&amp;id={vb:raw file.id}&amp;choe=UTF-8&amp;chld=L|4"></img>

..but the variable {vb:raw file.id} is not interpreted by vbulletin. (is simply ignored).

What can I do to correct this issue?
(I think this can be useful for many people, also for vb pages or cms articles)

Thank you in advance!
(And sorry for my bad english, but I'm italian)