Question about a scheduling application

I have an application that schedules weekly matches for a tennis club.

We schedule by this process:
Total the number of members and assign each person an random ID number between 1 and TotalMembers.
1 plays against 2, 3 plays 4, 5 plays 6, etc..

The problem now is that sometimes people play the same people 2 weeks in a row, or even soon after.
Does anyone have an idea so that we could fix this? Or even better schedule so that they loop through every player?
One thing to keep in mind is that the schedule is created each week because new members can be added at any time.

Thanks!