How to write a trigger in MS Access

Question

I´ve four tables.

• User
• Service
• UsedServices
• Permission

If I assign a user to a service (saved in UsedServices), I want to check with a trigger if the user have the permission (lookup in table permission if user exists) to use the service.

In SQL it´s easy to write a trigger for that, but I don´t have any clue how to realize that in MS Access.

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UPDATE:

UsedServices fields: ID | SERVICE

Permission fields: ID | SERVICE | FROM | UNTIL

If a person add a record in table 'UsedServices', then i want to check if the id is in table 'Permission' ans if the Permission is still valid from now.

Answer 1

To check if USER B have the permission in the 'Permission' table, use the BeforeUpdate event of the form:

Private Sub Form_BeforeUpdate(Cancel As Integer)

    Cancel = YourPermissionDeniedCheckFunction(Me!UserID.Value)

    If Cancel = True Then
        MsgBox "User " & Me!UserName.Value & " has not been granted the required permissions for this task."
    End If

End Sub