I am a bit stupid when it comes to Excel diagrams, so all your answers was
more than I understood. Here's what I want to do:

I want to create a diagram like this:
http://picasaweb.google.se/zitalena

Here are some of the values (the first 2 curves):

Capacity Sound pressure
178,5 56
206,3 56
240,9 58
278 58
308,1 59
369,9 59
420 60
480,1 60
482,3 61
556,9 61
549 61
648,4 61
616,2 62


149,5 49
169 49
200,3 51
230,4 51
255 53
303,8 53
349,5 53
395,6 53
400,6 54
460,2 54
476,4 55
535,5 55
509,9 56
607,6 56