InfoPath Dev

Got a form with a field that is suppose to be the employee ID How do I auto generate this - starting from 500000? Which is best - auto generate it on submit or on form load? How can I ensure that 2 end users don’t creates the same Employee ID?

 Where is the form submitting to? If submitting to a SharePoint form library, these have an ID column which autoincrements and could probably work as a unique employee ID within the library.

I believe that tou definitely want it to generate on submit. If two users open the form simultaneously, and the form opens and assigns them the next available ID, then they'll end up creating duplicates when they submit.

Submitting to a SP list ..can you tell me how to autoincrement

 This is an internal feature in SharePoint. Every list has an ID column which autoincrements for each item submitted.

yes I know - but if I want the employee ID to start with e.g 2000?