Given a set of databases how can one you get information on a book with given price first (which consist of the average of a hidden list of prices coming from different web site) and followed by an optional second option that shows the list of the different web site with their page?

To take an example given a query for ISBN 9785554443331 - it returns "Chemistry the central science 11 edition" : new:$50 used good condition:$35 used poor condition:$20

If the return does not match with our product list an option to "click here to visit our partner" appears and which returns:

Atextbook: $10
Btextbook: $10
Ctextbook: $9
Dtextbook: $8.50

I understand that the first search would be done simultaneous on the web and our database to determine whether or not we have the book and the web to get the average of the price of a given list of web site.

Thank you in advance for the help