This is called Record Level Access control and you can do this in Manage | Security. The Filemaker Help system gives you a pretty good description of the process, but it can be hard to find. Look up "Editing record access privileges" and scroll down to the section titled: "Entering a formula for limiting access on a record-by-record basis"
Is there any other way of locking a fields down after data has been added?
I have a holiday log system, where users can add there holiday requests. I want to ensure that after they've added a request and pressed a button to submit (which sends an email to managers to notify) and status changes to submit that the users cant change the date fields, id like them to lock from editing.
Managed to figure this out.
I used script triggers on the date fields to show custom dialogue box if status = "Submitted" or "Approved" to revert changes without dialogue. So no choice given to users to cancel the popup. trying to manually type the date or choose drop down is allowed. only when creating a new request can dates be changed :)