ปัญหาที่เกิดคือ ชื่ออาจาร์ยไม่ยอม Update เวลาเราเลือก รหัสอาจาร์ยใหม่นะครับ ขอบคุณครับที่เข้ามาช่วยตอบ
Option Compare Database
Option Explicit
Dim Mydb As Database
Dim MyRst As Recordset
Dim MyRsTeacher As Recordset
Dim MySql As String
Private Sub cbobinnumber_AfterUpdate()
MyRst.Seek "=", cbobinnumber.Value
MySql = "SELECT Teacher.TeacherID, ([forenames] & ' ' & [surname]) AS NameTeach FROM Teacher;"
Set MyRsTeacher = Mydb.OpenRecordset(MySql)
If MyRst.NoMatch = False Then
txtteachername.Value = MyRsTeacher.Fields("nameteach").Value
txtappnum.Value = MyRst.Fields("Appno").Value
txtExamDate.Value = MyRst.Fields("ExamDate").Value

Else
txtteachername.Value = Null
txtappnum.Value = Null
txtExamDate.Value = Null

End If
End Sub

Private Sub cbobinnumber_GotFocus()
Me.cbobinnumber.Requery
txtteachername.Requery
End Sub

Private Sub Cmdexit_Click()
DoCmd.Close
End Sub

Private Sub Form_Load()
Set Mydb = CurrentDb()
Set MyRst = Mydb.OpenRecordset("Registration")
Set MyRsTeacher = Mydb.OpenRecordset("Teacher")
MyRst.Index = "id"

End Sub

Private Sub Form_Unload(Cancel As Integer)
Mydb.Close
End Sub