english text spinner service

I have a visual basic 6 project that process english text,but I need that these text change automatic with similar text. I mean a spinner that change words per synonymous for make a text a unique content, I found many sites that make it but when I try these sites, the content is changed always with same synonymous, I need a spinner that have many synonymous for a word, then each time that I put a text change it to unique content. I need it work with service like an API that I can connect my vb6 code to this service. Don't matter if you recommend me a sites that I need pay a membership, but I need it work fine. More info by freelancer chat.