I thought of several things reading that post, see if any match your intended question.
The account is going to expire in 1 day or expired the previous day and you want to know how to have the account automatically suspend.
This would have to be done by an automated method of your choosing. By your billing software for example.
Since you mention ftp and calculate you want to know how to get accounts to automatically suspend once they've passed their quota.
It's possible but only happens when the tally is run, by default every 24 hours.
From either the admin or reseller level, change the details for the user account in question and check the box labeled "Suspend at Limit"
If those didn't answer your intended question, rewording it a bit (ok, alot) better would really help.