Count unused paragraph styles

I would like to audit my students' InDesign documents to find out if they have been tidy with their stylesheets. I have a script that partially works (I think it will work in CS4 as well, if you change CS5 to CS4).

The bit that won't work is trying to record the styles that are within groups. I have commented in the script to show the error section. I get the error:

"Invalid value for set property 'applied paragraph style'. Expected string, paragraph style or nothing, but receved \"body text (body)\"."number 30477

I was trying to put the style name and the group in, because that is the way it works if you do it manually, ie body text (body). But it doesn't work.

Any help would be appreciated.

property myTypeReport : "" -- makes it available everywhere
set myTypeReport to "" -- prevents the report becoming accumulative when running repeatedly
tell application "Adobe InDesign CS5"
   set myDocument to document 1
   set unusedStyles to ""
   set myFoundItems to ""
  
   set myDescription to "Unused paragraph styles"
   set myParagraphStyleGroups to every paragraph style group of myDocument
   set myParagraphStyles to every paragraph style of myDocument
  
   repeat with i from 3 to (count of myParagraphStyles)
       set myStyle to name of item i of myParagraphStyles
       set find text preferences to nothing
       set change text preferences to nothing
       set applied paragraph style of find text preferences to myStyle
       tell myDocument
           set myFoundItems to find text
           if (count myFoundItems) = 0 then set unusedStyles to (unusedStyles + 1)
       end tell
   end repeat
  
   -- this is the error section
   repeat with x from 1 to count of myParagraphStyleGroups
       set myGroup to name of item x of myParagraphStyleGroups
       set myParagraphStyles to all paragraph styles of paragraph style group myGroup of myDocument
       repeat with i from 1 to (count of myParagraphStyles)
           set myStyle to (name of item i of myParagraphStyles) & " (" & myGroup & ")" as string
           --return myStyle
           set find text preferences to nothing
           set change text preferences to nothing
           set applied paragraph style of find text preferences to myStyle
           tell myDocument
               set myFoundItems to find text
               if (count myFoundItems) = 0 then set unusedStyles to (unusedStyles + 1)
           end tell
       end repeat
   end repeat
   -- end error section
  
   set myReport to "(" & unusedStyles & ")" & "\t\t" & myDescription
   if (count unusedStyles) > 0 then set myTypeReport to myTypeReport & myReport & return
   return myTypeReport
end tell