Hello Nicholas,
maybe that it's a bit late but I've found that for this kind of things, 
OpenRefine (ex Google refine) works fine if the catalog you want to 
query allows passing parameter in the url; You can get the HTML code of 
the catalog pages and easily detect if it show a record or not. I've 
done it for different projects and found it a good answer to this problem.

You can then replay the scenario with openrefine on a new set of data / 
isbn. I don't know if it can be scripted but as shown after the 
paragraph starting with "So now we have our cleaned data file" on this 
blogpost : 
http://blog.ouseful.info/2013/07/26/using-openrefine-to-clean-multiple-documents-in-the-same-way/ 


Hope this helps.

Sylvain



Le 13/08/2014 12:20, Nicholas Brown a écrit :
> Apologies for cross posting
>
> Dear collective wisdom,
>
> I'm interested in using automation software such as Macro Express or iMacros to feed a list of ISBNs from a spreadsheet into Copac or Worldcat and output a list of those that return no matches in the results screen. The idea would be to create a tool that can quickly, although rather roughly, identify rare items in a collection (though obviously this would be limited to items with ISBNs or other unique identifiers). I can write a macro which will sequentially search either catalogue for a list of ISBNs but am struggling with how to have the macro identify items with no matches (I have a vague idea about searching the results screen for the text "Sorry, there are no search results") and to compile them back into a spreadsheet.
>
> I'd be keen to hear if anyone has attempted something similar, general advice, any potential pitfalls in the method outlined above or suggestions for a better way to achieve the same results. If something useful comes of it I'd be happy to share the results.
>
> Many thanks for your help,
> Nick
>
> Nicholas Brown
> Library and Information Manager
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