主题：[求助]想对下拉表的数据筛选下再下拉 总是有一个参数没有被指定值

Dim f1 As String = Forms("电容料号录入").Controls("ComboBox17").Value
Dim f2 As String = Forms("电容料号录入").Controls("ComboBox18").Value
Dim Filter As String
msgbox(f1)
msgbox(f2)
With DataTables("物料表")
Select Case f2
    Case "环氧"
      Select Case f1
        Case "散件"
        Filter = "Select *  f rom {行政区域} where [代码] like '______________________P%' And [代码]  Like '____________________B%'"
        Case Else
        Filter = "Select * f rom {行政区域} where [代码] like '_______________________P%' And [代码] Not Like "'____________________B%'"
      End Select
    Case Else
       Select Case f1
        Case "散件"
        Filter = "Select * f rom {行政区域} where [代码] like '______________________P%' And [代码]  Like '____________________B%'"
        Case Else
        Filter = "Select * f rom {行政区域} where [代码] like '_______________________P%' And [代码] Not Like "'____________________B%'"

      End Select
End Select
End With

DataTables("物料表").SqlLoad(Filter)

其中前面一个长线表示23个'_'，后面一个长线表示20个'_'