you will want to set up a search in the client with it looking for a document/folder with one of the specifiied ID's. You will need that advanced search syntax. Then you will need to use the '|' character between that and a copy of itself to send 2 or more ID's into the search and have it return those ID's. use the '|' character between each copy of that search syntax, each time changing the ID for the new pasted value.

Use the information in the link below to create the search URL

http://www.laserfiche.com/support/webhelp/webaccess/9.1/en-us/WA/WebAccess.htm#SearchURLs.htm%3FTocPath%3DURLs%7C_____3

and don't forget to change up the special characters, like this:

www.laserfiche.com/support/webhelp/webaccess/9.1/en-us/WA/WebAccess.htm#URL Encoding Reference.htm%3FTocPath%3DURLs%7C_____4