Code

 private: String^ chekSum(String^ DtCS) // data to chekum
         {
                 long  sum, i, a, b;

                 for(i=0; i<=10; i++)
                     sum = sum + (long)DtCS[i];

                 a = sum/256;
                 b =  sum - (a*256);

                 if(b>=64)
                     b=b-64;

                 b+=64;
                 a+=64;

                 return String::Format("{0}{1}",Convert::ToChar(a),Convert::ToChar(b) );
        }