Since then I have found the script by Lyndon at A new Bookends –> DT script with a group per reference and I am hopeful that a modified version of this script, using parts of a script by Lyndon Drake, using pieces from another script that Jim Neymann posted for for exporting data from Bookends to DTP, will do what I want. In short, it enable to search simultaneously both references I have processed in Bookends and ones that I have not yet processed, hopefully enabling me to identify which ones need to be processed.