league team matches

I'm looking for a way to determine what teams in a league play each other each week. Each team needs to play every other team once, and only once, before the league is done. I need to be able to do this for any number of teams.
I'm guessing that this needs to be done in a macro, but formulas would be fine also.

Example:
If I have 10 teams:
In week 1
Team 1 plays Team 2
Team 3 plays Team 4
....
Team 9 plays Team 10

In week 2 I thought this would work.
Team 1 plays Team 3
Team 2 plays Team 4
Team 5 plays Team 7
Team 6 plays Team 8
but that leaves Team 9 to play Team 10 again.

And the problem gets harder and harder each week.

just bumping to top