This is an extremely confusing question. Usually, that implies the person asking it is also confused.
It sounds like you have a population of 1000 samples from a normal random variable. For example,
z = randn(1,1000);
So the vector z will have 1000 samples. Now, do you want to do something with only those samples that lie in the interval [1,2]? If so, then you could just use find, testing if z>=1 and z<=2. Even simpler is just this:
z12 = z(z >= 1 & z <= 2);
If that is not what you are looking to see, then you need to VERY clearly explain your problem.