First of all are you aware that the range for a signed short integer is between -32767 and 32767. If this is adequate for job then the next series of question would be is how is this being used/inputed/stored.
Not knowing specifics Two ways come to mind:
1. Using the database/triggers/procedures create your own auto increment.
or
2. Programmatic means issue a query to yous data source max(yourfield) + 1
If you are mobile and disconnected from your data store that create other additional difficulties. As an example I have Bridge Inspectors that go out and Identify Bridge Maintenance needs. Each "Need" must be a unique number but I cannot tell or give the number out in the field. So to get around this -- each mobile app (my case an excel spreadsheet) generates a "local" unique Identifier. When the local data is submitted to me and after Q/A I upload this data to the central repository - Part of my upload process generates the "Next" available unique number to the Need by programmatic means. The Q/A'd application then assigns the local data the "official" Unique Value.
Hopefully this will trigger some ideas to get you unstuck.....
