Hi,
1. why did you ignore the questions at the beginning?
2. How is it to work?
Imagine there are 100 respondents at the same time.
Now one respondent enters "12345"
10 seconds later another respondent enters "12345".
Now the first respondent decides not finish the survey and he closes his browser.
So was the second respondent allowed to enter the number or not?
And if you only take into account completed surveys; as long as respondent 1 did not complete another respondent is able to enter the same number.
This you have to consider.
Anyway:
This could be useful (last example)
[url]
www.limesurvey.org/manual/StatFunctions
[/url]
But what is the reason to enter a unique number?
If you only want to generate a unique number, you'd better use the SAVEDID.
Joffm