You have to check all the BE tables one by one and see if they are all linked in the FE.  There is no shortcut, I'm afraid, but the code may not be too bad.  Get a list of all the tables in the BE (using a TableDef loop, for instance).  Then on the FE, use OpenRecordset to check if each BE table exists (i.e. is linked):

    Dim r As Recordset
    Set r = CurrentDb.OpenRecordset("BE table name")

If the above returns an error, that means the BE table doesn't exist (i.e. isn't linked) in the FE.  In that case, you link this BE table in your FE with:

    DoCmd.TransferDatabase acLink, "Microsoft Access", "C:\My Documents\BE.accdb", acTable, "BE table name", "FE table name"

Use a loop to do this for all the BE tables.  

If you have a lot (hundreds) of BE tables, this process could be slow.  If tables are frequently added, I suggest you log every addition in a table, so you have a list of newly added tables.  Otherwise, you have to look up BE tables one by one every time to find out which are new.