He wants to refer his claim against a Muslim to a kaafir court
Question

                I started a small business and I gave a Muslim brother some of my products to sell. This was about a year ago. The brother claims to have sold all of my products but he hasn't given me any money. I have been asking him for months now to give me my money.  He always claims to be "too busy" to come by and give me my money. However, he has all the time in the world to visit and mingle with kaafirs outside of his being "busy".  What should I do to get my money back?  I was thinking about taking him to small claims court. Is it Halal to sue your Muslim brother?  Also, can I make dua against this brother?  If so, can you give me the duas and some advise?
Praise be to Allah.You 
          could take him to court. If there is a sharee’ah court there, then praise 
          be to Allaah. Otherwise you can take to him to a court of the country 
          in which you live, but only after exhausting all possible means of getting 
          back what you are owed, such as getting other people to mediate in the 
          matter.   
With 
          regard to praying against him, if it is quite clear to you that he intends 
          to take your property wrongfully, then you have the right to pray against 
          him.