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

yes, i have see that article.. but i believe that there must exist a code or a function in excel somewhere. my proof is that Excel draws the smooth line for you. If excel can do that there must be some sort of coordinates for every little turn on the smooth line, and thereby coordinates for the relative maximum (in my example, on the graph, around 1,360:52).
the FORECAST function sometimes work, but not in all conditions.
I know it's not a easy problem to solve, since I've been working on it all weekend.

best regards
Hans