creating a list

Hi,
Please tell me how I would calculate the right column.
For each error list the hosts that have that error.
Column 3 is the unique hosts
Column 4 is the unique errors
------- --------- -------- ---------- ----------------------------------
host2 error03 host1 error03 error03 on host2
host3 error10 host2 error10 error10 on host3, host4
host4 error10 host3 error11 error11 on host2, host3
host2 error11 host4 error12
host3 error11 host5 error14
host3 error12 host6 error15
host5 error12 host7 error16
host4 error14 -------- error17
host5 error15 -------- error22
host5 error15 ------- error23
host6 error16 ------- error32
host7 error17 ------- error33
host3 error22 ------- error34
host4 error22
host3 error23
host4 error23
host6 error32
host4 error33
host4 error34

Thanks,
Jim