Is there an easier way to capture hdr picture with taking one picture, then changing the exposure on a softwar?

I have the d3000 from nikon and it doesnt have exposure bracketing. im also getting frustrated if i take them manually (changing exposures) because sometimes the camera will move (i dont have a tripod, im only 14) so, i was thinking maybe i can take a picture of a field, then adjust the exposure of 1 of the copies of the picture to really high, and the other one really low, and the last one in the middle range, then i can use photomatix to put them together. what do you think , and will this work? thanks.