You're not going to get away without coding anything. I've never tried using barcode scanners with Access forms, but I daresay that that will be the simplest part of it.
With regard to checking the ticket, I would advise that you use a recordset. This will allow you to perform one pass over the table, and from that pick up all of the required fields for analysis and updating. The following air code assumes that the scanner dumps the code into a field call txtBarcode, your table is called tblTickets and the form is unbound. The form has fields txtName and txtWarning. You will also need to set up a link to the MS ADO library (in the VBA editor, it's Tools -> References).
You might want to do more with it, but that should get you started.
Private Sub txtBarcode_AfterUpdate()
Dim rstTicket As ADODB.Recordset
Dim strSQL as String
Set rstTicket = New ADODB.Recordset
strSQL = "SELECT [Name], [Ticket Sold], [Ticket Entered] FROM tblTickets WHERE [Ticket Scan] = '" & txtBarcode & "'"
rstTicket.Open strSQL, CurrentProject.Connection, adOpenDynamic, adLockOptimistic
If rstTicket.EOF Then
'This barcode was not found in the table
txtWarning = "Invalid ticket!"
'The ticket exists. Has it been sold?
If Not rstTicket![Ticket Sold] Then
txtWarning = "This ticket has not been sold yet!"
'Has the ticket already been used?
If rstTicket![Ticket Entered] Then
txtWarning = "This ticket has already been used!"
'So, the ticket exists, has been sold and has not been used. Record its use and display the holder's name.
txtName = rstTicket![Name]
rstTicket![Ticket Entered] = True
Set rstTicket = Nothing
10% of magic is knowing something that no-one else does. The rest is misdirection.