主题：Up date语句执行出错

“物流表”中的“实际数量”列改变后，会自动修改库存中的相应物料的“数量”，使用的是ACCESS外部数据源。问题是：每次在物流表中新增行后，第一次执行up date语句时会报错，“标准表达式中数据类型不匹配”；我看了下表的列类型都是“单精度小数”，关掉报错后再修改当前行的“实际数量”列，就不会报错了，库存数量也会改变了，请教各位，这是为什么呢？

Dim cmd2 As New SQLCommand
Dim dt2 As DataTable
cmd2.C
cmd2.CommandText = "SELECT * F rom {Store}"
dt2 = cmd2.ExecuteReader()

select case e.DataCol.Name

Case "实际数量"
        e.DataRow("出入库时间") = Date.today()
        If e.NewValue IsNot Nothing Then
            Dim dr As DataRow
            dr = dt2.Find("[物料编码] = '" & e.DataRow("物料编码") & "'")
            Select Case e.DataRow("出入库方向")
                Case "入库"
                    If dr IsNot Nothing Then
                      cmd.CommandText = "Up date {Store} Set [数量] = [数量] + '" &  e.NewValue & "' - '" & e.OldValue & "' Where [物料编码]= '" & e.DataRow("物料编码") & "'"
                      cmd.ExecuteNonQuery()
                    End If
                    If dr Is Nothing Then
                        Dim dr1 As DataRow = DataTables("Store").AddNew()
                        dr1("物料编码") = e.DataRow("物料编码")
                        dr1("属性") = e.DataRow("类别")
                        dr1("名称") = e.DataRow("名称")
                        dr1("图号") = e.DataRow("型号")
                        dr1("单位") = e.DataRow("单位")
                        dr1("数量") = e.NewValue
                        dr1("库存下限") = 0
                    End If
                   
                Case "出库"
                    If dr Is Nothing  Then
                        MessageBox.Show("库存中无此编号的物料,请确认编号再领取!")
                        Return
                    End If
                   
                    If dr IsNot Nothing Then
                        If dr("数量") < e.NewValue - e.OldValue Then
                            messagebox.Show("库存不足,请修改!","提示")
                            e.cancel = True
                        End If
                        If  dr("数量") >= e.NewValue - e.OldValue Then
                            cmd.CommandText = "Up date {Store} Set [数量] = [数量] - '" &  e.NewValue & "' + '" &  e.OldValue & "' Where [物料编码]= '" & e.DataRow("物料编码") & "'"
                            cmd.ExecuteNonQuery()
                        End If
                       
                       
                    End If
            End Select
            DataTables("Store").save()

end select