I don't know if it replies to your question, but you can exclude all files with the extension ".Junk".
For creating a global exclusion list for a specific file extension on every backup job, go to:
>Edit | Edit Selection List
>Select the Excludes selection list, and click Edit
>With the Excludes Properties box open, click Insert
>In the Advance file selections box, Specify the Path field. Then add the extension to the File field.
For excluding a specific file extension on a specific backup job, go to:
>Job Properties.
>On the Selections tab, click Advanced
>In Type, select Exclude radio box, and specify in the file field the extension to be left out.
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