I have a table in which number details of document is stored. For example, for invoice, number range is 101 to 105. Now when this range ends (invoice no 105 created). At that time, Pop-up alert is shown to user to set the range again. When he sets range for invoice for 2nd time, he should not be able to set old range i.e. 101-105 again.
How can I check this ?