This article applies only to a Microsoft Access database (.mdb).
- User/Group accounts and permissions
- Database passwords
NOTE: The sample code in this article uses Microsoft Data Access Objects. For this code to run properly, you must reference the Microsoft DAO 3.6 Object Library. To do so, click References on the Tools menu in the Visual Basic Editor, and make sure that the Microsoft DAO 3.6 Object Library check box is selected.
Using Code to Password Protect a FormBy using code, you can prompt for a password when a user opens a form or a report. If the correct password is entered, the form or the report is opened.
The following example shows you how you can password protect the Orders form in the sample database Northwind.mdb:
- Start Access and then open the sample database Northwind.mdb.
- Press ALT+F11 to start the Microsoft Visual Basic editor.
- On the Insert menu, click Module.
- In the module sheet, type the following procedure:
Public Function KeyCode(Password As String) As Long
' This function will produce a unique key for the
' string that is passed in as the Password.
Dim I As Integer
Dim Hold As Long
For I = 1 To Len(Password)
Select Case (Asc(Left(Password, 1)) * I) Mod 4
Case Is = 0
Hold = Hold + (Asc(Mid(Password, I, 1)) * I)
Case Is = 1
Hold = Hold - (Asc(Mid(Password, I, 1)) * I)
Case Is = 2
Hold = Hold + (Asc(Mid(Password, I, 1)) * _
(I - Asc(Mid(Password, I, 1))))
Case Is = 3
Hold = Hold - (Asc(Mid(Password, I, 1)) * _
(I + Len(Password)))
KeyCode = Hold
- Press ALT+F11 to return to Access.
- In the Database window, under Objects, click Tables, and then click New.
- In the New Table dialog box, double-click Design View.
- Create a new table as follows:
Field Name: ObjectName
Data Type: Text
Field Size: 50
Field Name: KeyCode
Data Type: Text
Field Size: 25
Input Mask: Password
Table Properties: tblPassword
- Open the tblPassword table and then enter the following data:
- Create a new form in design view and save the form as frmPassword.
- Add a single textbox to frmPassword called Text0, and a command button called CheckPassword.
- Set the Input Mask property of Text0 to "PASSWORD" (minus the quotation marks).
- Add the following code to the OnClick Event of the CheckPassword button and then save the form:
If IsNull(Forms!frmPassword!Text0.Value) Then
MsgBox "You cannot enter a blank Password. Try again."
MyPassword = Me!Text0.Value
DoCmd.Close acForm, "frmPassword"
- Open the Orders form in Design view.
- If the property sheet is not visible, click Properties on the View menu.
- Type the following event procedure in the module for the OnOpen property of the form:
Private Sub Form_Open(Cancel as Integer)
Dim Hold As Variant
Dim tmpKey As Long
Dim I As Integer
Dim rs As DAO.Recordset
Dim db As DAO.Database
On Error GoTo Error_Handler
' Prompt the user for the Password.
DoCmd.OpenForm "frmPassword", acNormal, , , , acDialog
Hold = MyPassword
' Open the table that contains the password.
Set db = CurrentDb
Set rs = db.OpenRecordset("tblPassword", dbOpenTable)
rs.Index = "PrimaryKey"
rs.Seek "=", Me.Name
If rs.NoMatch Then
MsgBox "Sorry cannot find password information. Try Again"
Cancel = -1
' Test to see if the key generated matches the key in
' the table; if there is not a match, stop the form
' from opening.
If Not (rs![keycode] = KeyCode(Cstr(Hold))) Then
MsgBox "Sorry you entered the wrong password." & _
"Try again.", vbOKOnly, "Incorrect Password"
Cancel = -1
MsgBox Err.Description, vbOKOnly, "Error #" & Err.Number
- Close and then save the Orders form.
- Open the Orders form and then type PASSWORD when you are prompted for a password.
Notice that the Orders form opens. The KeyCode that is generated by PASSWORD matches the KeyCode in the tblPassword table, and is dependent on the case of the letters in the password entered.
- Close and then reopen the Orders form and then type PassWord when you are prompted for a password.
Notice that you receive the message:Sorry you entered the wrong password. Try again.The Orders form does not open because the password procedure is case-sensitive.
- To determine what the corresponding KeyCode is for a particular string, type the following in the Immediate window and then press ENTER:The earlier example returns 5864.
- To hide the tblPassword table in the Database window, right-click the tblPassword table, and then click Properties. In the Properties window, click to select the Hidden check box, and then click OK.
รหัสบทความ: 209871 - การตรวจสอบครั้งสุดท้าย: 23 มิ.ย. 2005 - ฉบับแก้ไข: 1