Search for previous posts about numbering sequences.

In SQL you can create a field named autonumber and it will increment 1 each
time a record is added.

You cannot create a number before a record is created though

Hello,

You can also generate unique GUID in Load event using "Scriptlet.TypeLib"
ActiveX object (if you are in JavaScript):

var guid =
new ActiveXObject("Scriptlet.TypeLib").guid.substring( 0, 38);

or using System.Guid.NewGuid() method (if you are in .NET).

Assign this guid to your Leave_ref_number for employee.

I hope this will help for you.

Hello

Did you want to create a unique number based on some fields value in your
form?