There's no way to do that using Opus itself but you could do it using a scripting language (e.g. VBScript or JScript).
You can call Opus commands from outside of Opus using "dopusrt.exe /cmd " and the commands for adding files to collections are listed in this thread:
[Is DOpus right for me?:: user-generated collection xml)
Having the script remove old and invalid items from the collections list could be more difficult since it would have to know what's in the list... The collections are stored in XML files so the script could parse them but I think it would be easier for the "Clean Up" mode of the script to completely delete all the collections and then re-create them.