PMFJI,

The problem is that you used spaces and special characters when you named
your objects. As you have found, spaces in names of objects causes you
headaches.

Since you have spaces in the names, you need to enclose them in brackets:

Try this:

Sselect * from [Client Master File] Where [ID] = forms![Processing - Select
Client].
[Processing Client List]

If you must separate words, use the underscore  Client_Master_File

This is another way  (no spaces) >>   ClientMasterFile

Also, search the web for "naming conventions". Here is one page:

http://www.mvps.org/access/general/gen0012.htm

A consistant nameing convention makes it easierto tell what the object is

if the object is then the prefix is

     table ............ tbl
     form..............frm
    listbox............lb    (lower case L )

So the recordsource would look like:
(should be one line)

Sselect * from tblClientMasterFile where [ID] =
forms!frmProcessingSelectClient.lbProcessingClientList

Just remember - if you use spaces in object names, enclose them in brackets :)

BTW, form "Processing - Select Clients" must bo open when you open form
"Processing Detail".

HTH