High level record lock

Is there a way to 'lock' a record so that nothing can even read it until I release it?

We have a control record for next-available-group-number. We read the record to get the next number, and then increment the number and update the control record. This works fine until we hit the situation where two jobs read the control record virtually simultaneously, and the faster job burns through the next 6 available numbers before the slower job does its first update, even though this happens in a tiny fraction of a second. It's literally a million-to-one chance, but it just happened last week.

Once a job reads the control record, I need to prevent any further access of the record (including reads) until the first job releases it.

I've thought about trying to use a single SQL update statement but there are two problems with that:
1. The 'number' is in an alpha field that I have to substring to get, and to update.
2. The 'number' is 5 digits and will have to eventually wrap around from 99999 back to 1.

I can't lock the file.

We're on 7.2.

Any thoughts?

Thanks.

~TA~