so many great solutions, thank you all!

one step further: after aggregating the data I was looking for a nice
way to show what it is made of - similar with the double click on a
cell in a pivot table. so I found this code  for a cell double click event:

Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
If Not Intersect(Target, Range("b2")) Is Nothing Then
Sheets.Add

..and here i would like to do what the pivot-table does when you
double-click a cell, i.e. to copy only the rows used in the
computation of that cell (I also recorded a macro while
double-clicking the pivot table but..the part which filters and copies
the rows is missing from the code).

any ideas how to do this?