script search for text in table

Usethe following script.It does not findtext in tables, howcan I do tofindtextin all tables?
How do I searchand inserttabandreturn?
Thanks to all and sorry formy english

tell application "QuarkXPress"
    set t to count documents
    repeat with i from 1 to t
        try
            tell document 1 of application "QuarkXPress"
                set (every text of every story where it is "cat ") to "dog "
                set (every text of every story where it is "red") to "blue"          
            end tell
        end try
        save document 1
        close document 1
    end repeat
end tell