When original data are periodically read from Excel, then autonumeric ID's for trainers and students are probably out - unless you register trainers and students in Access DB, and those registers are read into Excel.
In case you can't/don't want to move all data management into Access, you probably have to design a proper structure for Excel part too. Possible variations:
1. Trainers and students registers are kept in Access [tblTrainers: TrainerID, TrainerForename, TrainerLastName, ...; tblStudents: StudentID, StudentForename, StudentLastName, StartYear, CurrentClass, ...). Both registers are read into Excel file(s) using ODBC queries, where additionally is calculated a FullName field in format like <LastName & " " ForeName & " (" & ID & ")". (ID is added for cases there are trainers/students with same fore- and last names). In Excel data entry table(s), users can select FullName (you use Data Validation List with dynamic named range based on FullName column of according query table). In data entry table must be a column(s), where TrainerID and StudentID are calculated. And when you'll keep Excel table(s) on predetermined network resource(s), you can link Excel table(s) into your Access DB. You can create a procedure in Access DB, which you can run at any time you want, and it updates your Access data, using query like
Code:
SELECT <FieldList> FROM LinkedExcelTable AS let LEFT JOIN YourAccessTable AS yat ON yat.TrainerID = let.TrainerID AND yat.StudentID = let.StudentID AND yat.EntryDate = let.EntryDate WHERE yat.TrainerID Is Null
2. Trainers and students registers are kept in Excel. In this case, it's best to have a single Excel file, or a master Excel file where trainer and student registers are maintained. When you have a master file, you must read both registers into user(s) Excel file(s) using again ODBC, or link formulas. Following will be same as p.1.
It is best you link into access Excel files where real data entries are made - when you link some summary file to where data is read from data entry files, then before you read new data into Access DB, you have to open and requery this summary Excel file.