How to add two random numbers within a range?

My requirement :--

The sum of the two random numbers will be 100..
      sum=random_no1 + random_no2  (the sum will be exact 100)

So,I have tried:--

Random r = new Random();
        int Low = 10;
        int High = 100;
        int R = r.nextInt(High-Low) + Low;

    Random r1 = new Random();
    int Low1 = 10;
    int High1 = 100;
    int R1 = r1.nextInt(High1-Low1) + Low1;

but how I define the sum??

I can not understand..Please help me..