I suggest you use an auto-entered serial number field instead. This is a built in feature you can easily use and it is designed to generate unique values even when several users are all accessing your database and created new records all at the same time.
What you describe can be done, but in a multi-user environment, it is quite difficult to ensure that two users can't do this at the same time and thus get the same, duplicate value for a lot number.
You can certainly define such a field and use it for search/sort/identification purposes, but I wouldn't use it in relationships to link to other data tables.
Here's an auto-enter expression:
Left ( Namefield ; 3 ) & Get ( CurrentDate )
If you don't want to see the date divided by / characters, use a substitute function call to remove them:
Left ( Namefield ; 3 ) & Substitute ( Get ( CurrentDate ) ; "/" ; "" )
I'd add a validation rule to specify unique values on this field to catch cases where a second new record is created with the same 1st three letters on the same date.
Hey Thanks, that helped a ton!