How can I avoid duplicate data entry?

[Gsantacruz]

Hello,

I have a form that i need operators to fill in with how many hours they worked that day (they enter the date, their name and the hours). They have been entering the data more than once, which really messes with my calculations. I have been trying to use a before update event in my Hours textbox with a message box telling them that they already entered the data and cancelling the entry, but i cant get it right. This is what I have: (please bear with me i'm a total newbie)

Private Sub Hours_BeforeUpdate(Cancel As Integer)
Dim icount As Long
icount = Nz(DLookup("Hours", "Inspectors' Hours", "Hours=" & Me.Hours), 0)
If icount <> 0 Then
MsgBox "You have already entered your hours for today."
Cancel = True
Undo
End If
End Sub

Thank you for your time!!

[Mariostg]

Create a primary key using two fields: name and hours. See my post here:
http://bytes.com/topic/access/answer...on#post3606144