secondary axis chart
 

I have a line chart for which I have developed several point to point trend
lines which I would like to overlay on the original line chart. The points
are represented in four sets of series as follows:
Date1 Value1 Daten Valuen Datez
Valuez
Date2 Value2 Daten+1 Valuen+1 Datez+1
Valuez+1

Date3 Value3 etc. etc.
Date4 Value4

etc.

I tried to set each of the sets up as scatter charts specifying the primary
x axis. That is strictly hang time. I tried to set up each pair of points
as separate series(that amounts to thirty of forty separate series). I
achieved the overlay but if I change the data(not the limits but the data
itself) I again hang; I suppose because the calculations that modify the
trend dates change the limits on those series. I left spaces between the
trends points because I don't want them connected. Any suggestions?

GeneS