按帮助中所写的操作EXCEL报表，但总是报错，如图

此主题相关图片如下：qq.jpg

打印代码如下：

Dim cb1 As winform.combobox=e.Form.controls("combobox1")
Dim cb2 As winform.combobox=e.Form.controls("combobox2")
Dim con As String="data"
If cb1.value isnot Nothing And cb2.value isnot Nothing Then
    With Datatables("导航_GCGMX")
        .loadfilter="[供应商]=\'" & cb1.value & "\' and [采购单编号]=\'" & cb2.value & "\'"
        .load
    End With
    If Tables("导航_GCGMX").count>0 Then
        Dim dt As Datatable
        Dim cmd As new sqlcommand
        cmd.connectionname=con
        cmd.commandtext="select * from 供应商信息 where 供应商名称=\'" & cb1.value & "\'"
        dt=cmd.executereader
        If dt.Datarows.count>0 Then
            vars("采购单_联系人")=dt.Datarows(0)("联系人")
            vars("采购单_电话")=dt.Datarows(0)("电话")
            vars("采购单_传真")=dt.Datarows(0)("传真")
        Else
            vars("采购单_联系人")=Nothing
            vars("采购单_电话")=Nothing
            vars("采购单_传真")=Nothing
        End If
        vars("采购单_采购员")=user.name
        vars("采购单_采购单编号")=cb2.value
        vars("采购单_供应商")=cb1.value
        vars("采购单_交货日期")=Datatables("导航_GCGMX").Datarows(0)("交货日期")
        Dim Book As New XLS.Book(ProjectPath & "Attachments\\采购单.xls")
        Dim fl As String = ProjectPath & "Reports\\采购单.xls"
        Book.Build() \'生成细节区
        Book.Save(fl) \'保存工作簿
        Dim Proc As New Process \'打开工作簿
        Proc.File = fl
        Proc.Start()
    Else
        messagebox.show("当前表没有可打印的数据!请重新筛选择打印数据!","提示")
    End If
Else
    messagebox.show("供应商名称,采购单编号不能为空值!请重新选择正确的打印选项后再生成采购单数据!","提示")
End If