I built a preview statement in the main form of button, add event process below code:
Private Sub preview reports _Click ()
On Error GoTo Err_ preview reports _Click
Dim ss As Long
Demand for a single number. SetFocus
Dim stDocName As String
Ss=demand a single number. The Text
StDocName="logistics demand list"
DoCmd. OpenReport stDocName acPreview, ""," [demand single number]="& amp; Ss & amp; "
"Exit_ preview statements _Click:
The Exit Sub
Err_ preview statements _Click:
MsgBox Err. The Description
Resume Exit_ preview reports _Click
End Sub



Then when child form input entry ITEM entry items, click on the preview report button will generate a few pages duplicate report, how to remove duplicate report