fencing on a slope

[genesis]

I wish to replace an existing fence with 8 Ft concrete posts and concrete 300cms high concrete panels at the base with 6Ft wide close boarded fence panels on top of the concrete panels, making a total height of 6 Ft to top of panels . The garden is level for about 4 panels then starts to slope for another 8 panels.
I want the height from the top of the panels to the top of the concrete posts to be constant on the flat and the slope. How do I do this, I have a friend to help me.
Sincerely
Alan N

[SparkoJon]

Use a piece of string and a level for the horizontal - once you have a level to work with you can adjust the depth required as you move down the garden.