Change method annotation parameter values

I am trying to change the test parameter description on run time. All the examples I have seen refers to changing annotation value at class level. But, I want to do it at method level.

My sample code is as below:

import org.testng.annotations.BeforeMethod;
import org.testng.annotations.Test;
import java.lang.reflect.Method;

public class TestClass {

    @BeforeMethod
    public void beforeMethod(Method method){
        Test annotation = method.getAnnotation(Test.class);
        // I want to change description to "some modified description"
    }

    @Test(description = "some description")
    public void test(){
        System.out.println("in test");
    }
}