Finding the relative maximum.

hello fellow excel coders ! :D

i have a problem for you guys to solve.
I am trying to find the relative maximum in a smooth graph, so that i can get the correspondent number out from it. (in my example around 52 degrees)
as you can see in the example i have added in a line to illustrate where and what number i want out of it..
hope i have giving you enough information's.

note: the numbers change as the ships stability change (GZ) so the maximum value can be at any of the giving degrees.

best regards
Hans