blending

I’m having laser treatments on my arms, and I have fine dark hair on the upper third of my arm that continues all the way up around my shoulders. I don’t want to end up with a line separating the part that wasn’t treated from the part that was treated. What is the best way to get a more blended-in look? Should I go a little higher with each treatment, or should I alternate (go higher up for my second treatment, then lower for my third, then higher for the fourth, etc.)?