The Find/Replace expression I provided will already do that. Running it once converts:
1
2
3
4
5
6
7
8
to:
12
34
56
78
Running it a second time will give you:
1234
5678
It won't remove extraneous lines between individual numbers or groups of numbers, though.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]