Yes you could open a recordset which identifies those people not on the Master.
Loop through the recordset, include a message to determine if person should be added or not
Here's a rough sample from some of my data: (Student has not yet selected a Course)
Code:
Sub testRS()
Dim rs As Recordset
Dim Resp As Integer
Set rs = CurrentDb.OpenRecordset("SELECT Student.id, Student.studentName, SelectedCourses.CourseId " _
& " FROM SelectedCourses RIGHT JOIN Student ON SelectedCourses.StudentId = Student.id " _
& " WHERE (((SelectedCourses.CourseId) Is Null));")
Do While Not rs.EOF
Resp = MsgBox("add " & rs!studentname & " to Master", vbYesNo)
If Resp = vbYes Then
MsgBox "Code to Add " & rs!studentname & " to Master goes here", vbOKOnly
' your code to add
'this record goes here
'
Else
MsgBox "Code to NOT Add " & rs!studentname & " to Master goes here, ignore this guy and get next ", vbOKOnly
'your code to ignore this record
'and move on goes here
'
End If
rs.MoveNext
Loop
End Sub
Good luck