Trace a global trend curve then other secondary

[geofad2000]

Hello everybody,
I have a file in text format (A), contains 391 values, I would like to make a plot with global trend curve.
I have another file BRP, which contains points with an index (between 02 and 03 points), I would also like to make trend curves between each two points (on the previous plot).
This operation I have to repeat it 50 times.