You've got a major design flaw, here. Your employee Form should actually be a Main Form, and your 'equipment issued' data should reside in a separate, related Table, and displayed in a Subform, with the relationship to the Main Table being a One-to-Many one.
The Main Table should contain everything you've listed except the equipment. There should be a Primary Key Field that is unique to each employee Record; I suppose that the SSN would work for this...although many prefer to use an Access generated Autonumber, serving no purpose except to uniquely identify a given Record.
The related Table that the Subform is based on should contain a Foreign Key that matched the Primary Key from the Main Table, and acts to tie these two Tables together.
The Subtable needs to have the Foreign Key Field mentioned, above, as well as Fields for all of the equipment related data...DateOfIssue (note no 'First' in that field...we'll address that in a minute) EquipmentIssued, the Cost, and an arbitrary ID number.
Rather than having a separate DateOfFirstIssue field, you should have a Boolean Field Bound to a Checkbox, on the Subform Record, that when checked indicates that this was the original issuance of the piece of equipment to a given employee.
The equipment Field could still be based on a Combobox, pulling the equipment data from your equipment Table. but each piece of equipment would be recorded in a separate Record, rather than all of it, for a given employee, being crammed in a single Field.
Each time you add a piece of equipment, you could run a DCount() against the underlying Table, seeing if that employee has already been issued that particular piece of equipment before.
Note that if you elect to have the PK in the Main Table as an Autonumber, then the matching FK Field, in the SubTable, needs to be defined as a Number (Long Integer) Datatype.
Linq ;0)>
The problem with making anything foolproof...is that fools are so darn ingenious!
All posts/responses based on Access 2003/2007