请看以下代码：

Dim nma() As String = {"产品成本价","订单编号","供应商名称","产品名称","产品数量","产品票面价","产品批号","仓库名称","入出库类型"} \'A表数据来源列
Dim  nmb()  As  String = {"产品入仓成本价","订单编号","供应商名称","产品名称","产品数量","产品入仓票面价","产品批号","仓库名称","入出库存类型"} \'B表数据接收列
Dim tr As DataRow
With DataTables("库存明细表")
     tr = .Find("订单编号 = \'"& tables("订单明细表").Current("订单编号")&"\'")  \'找出最后一次订购PD01产品的记录
    End With
If tr("订单编号")="" Then

For Each r As Row In Tables("订单主表.订单明细表").Rows
    Dim dr As DataRow = DataTables("库存明细表").AddNew
    For i As Integer = 0 To nma.Length - 1
        dr(nmb(i)) = r(nma(i))
    Next
Next
End If

代码看不出问题，至少要说一下错误提示啊，当然有个小例子就更好了。

请看六楼

错误原因是，当你没有找到tr这一行的时候，对象就是空，就导致错误了

楼主您看看：

http://www.foxtable.com/help/topics/2044.htm

要加上判断，因为不一定总是有符合条件的行：

Dim nma() As String = {"产品成本价","订单编号","供应商名称","产品名称","产品数量","产品票面价","产品批号","仓库名称","入出库类型"} \'A表数据来源列
Dim  nmb()  As  String = {"产品入仓成本价","订单编号","供应商名称","产品名称","产品数量","产品入仓票面价","产品批号","仓库名称","入出库存类型"} \'B表数据接收列
Dim tr As DataRow
With DataTables("库存明细表")
    tr = .Find("订单编号 = \'"& tables("订单明细表").Current("订单编号")&"\'")  \'找出最后一次订购PD01产品的记录
End With
If tr IsNot Nothing Then
    If tr("订单编号")="" Then
        For Each r As Row In Tables("订单主表.订单明细表").Rows
            Dim dr As DataRow = DataTables("库存明细表").AddNew
            For i As Integer = 0 To nma.Length - 1
                dr(nmb(i)) = r(nma(i))
            Next
        Next
    End If
End If

另外建议卡看这个

http://www.foxtable.com/help/topics/1485.htm

这样遇到问题，可以快速找出出错的代码