You can create a self-relationship for that table, where:
Vessel = Vessel
ID does not equal ID
You can sort that relationship in descending ID order, or use the Max () function to find the previous highest value, and check against that.
The records are linked by a vessel name
This is not a good idea. What will you do if you get two vessels with the same name? What will you do if someone misspells the vessel's name and you con't catch the error until after you have created related records in the portal?
The Vessels table needs a unqiue, auto-entered ID, such as fileMaker generated serial number as that way you avoid these issues.
Yeh sorry Phil, I was suppose to write "linked by vessel ID" which is what I have. What I forgot to add in the original post is that it is not just the previous record of the database...it is the previous record from a specific vessel. So how would I be get the field value "total running hours" from the previous record from that vessel? Do I have to find the vessel ID? If so, how do I do a generic find when I am seaching for the one vessel?
My advice would match Sorbsbuster here, but use EquipmentID instead of VesselID. Where Equipment ID uniquely identifies one piece of equipment installed on one specific vessel. Referring by memory to other posts, that ID field would be the primary key field used in your EquipmentList table.
ServiceLog::_fkEquipementListID = ServiceLog 2::_EquipmentListID AND
ServiceLog::__pkServiceLogID ≠ SerivceLog 2::__pkServiceLogID