Sorry, not at the moment. Planned to be added to the next version.
Meanwhile, you can do it 'by hand', though.
The easiest way is to go to the chest folder (typically <avast-folder>\Data\Chest), open the index.xml file and find the ID of the corresponding file. The infected file itself will be stored in the chest folder as well, with the ID used as the file name. It is encrypted, but you can send it to us in this form, we'll manage...
Thanks
Vlk