Cancel Adding New Record If Condition Is True

Hi

I wrote code that should validate a field when entering a new record and then if a condition is true, that new record should be cancelled and not entered into the table.

I managed to partially achieve this by writing the code below, but the new record does not get cancelled because the table will still create a PK for that record and leave the rest of the fields empty. I am using an autonumber for the PK that's why the table creates it automatically What I want to achieve is to cancel the creation of a new record at once, I don't want even PK created for that new record.

I used the CancelUpdate because I thought it would cancel the record creation, but it did not! When I read about it it said that I need to use it with either Edit or AddNew, (which i don't understand why!) but it still does not work.

Private Sub PlotNum_BeforeUpdate(Cancel As Integer)
On Error GoTo Err_msg
Dim db As DAO.Database, rs As DAO.Recordset
Dim n As Integer, i As Integer
Dim vPlotNum As Integer
Dim vPhaseID As Integer

vPhaseID = Forms![frmHouse].Form![PhaseID]
vPlotNum = Forms![frmHouse].[qryHouse2].Form![PlotNum]

Set db = CurrentDb
Set rs = db.OpenRecordset("tblHouse")
rs.MoveLast
n = rs.RecordCount
rs.MoveFirst
If n > 0 Then
For i = 1 To n
If rs![PhaseID] = vPhaseID Then
If rs![PlotNum] = vPlotNum Then
rs.Edit
rs.CancelUpdate
MsgBox "This plot number already exist in this particular phase." & vbCrLf & "Please choose a different Plot Number"
Forms![frmHouse].qryHouse2.Form![PlotNum].Text = ""
End If
End If
rs.MoveNext
Next i
End If
rs.Close
db.Close
Set db = Nothing
Set rs = Nothing

Exit_Err_msg:
Exit Sub

Err_msg:
MsgBox Err.Description
Resume Exit_Err_msg
End Sub


Any suggestions will be very much appreciated.
Thanks.
B