Hello, I am wondering if there is a way to do something like this:

What I currently have:
......................Customer1................Customer2.........
...........data1....data2....data3....data1....data2....data3
Item 1.....aa.........bb.........cc........dd........ee.........ff
Item 2.....gg.........hh..........ii..........jj.........kk..........ll
Item 3.....mm........oo.........pp.........qq........rr..........ss

What I need:
................................data1....data2....data3
Item 1....Customer1........aa........bb.........cc
Item 2....Customer1........gg........hh..........ii
Item 3....Customer1........mm.......oo.........pp
Item 1....Customer2........dd........ee..........ff
Item 2....Customer2.........jj.........kk...........ll
Item 3....Customer2.........qq........rr..........ss