UPDATE TabloAdı SET Talep=clng(nz(ÖnGörü,0)) WHERE (((ÖnGörü)>0))

Sub dugme_click()
Dim kyt As Recordset
Set kyt = CurrentDb.OpenRecordset("SELECT ÖnGörü, Talep FROM TabloAdi SET Talep=clng(nz(ÖnGörü,0)) WHERE (((ÖnGörü)>0)) ")
If kyt.RecordCount = 0 Then Exit Sub
Do Until kyt.EOF
kyt.Update
kyt!TALEP = kyt!ÖnGörü
kyt.Update
kyt.MoveNext
Loop
kyt.Close
Set kyt = Nothing
End Sub

Private Sub SetAll_Click()
Dim Sw As Long
For Sw = 1 To Me.Recordset.RecordCount
    Me.Talep = Nz(Me.ÖnGörü,0)
DoCmd.GoToRecord , , acNext
Next Sw
End Sub