Has anyone ever tried to control or manipulate the course of their dreams, while dreaming?

Ever since I was 9 or 10 I have been an active dreamer. It doesn’t always work, and sometimes I don’t want to change the course of a dream.

I’m not talking about using outside stimuli to influence dreams. I’m referring to a semi-conscious state within a dream when 1) you realize that you are dreaming 2) within the dream (from the inside) you attempt to change the course of your dream.