查询access的老是提示参数不足

我查询access（97）的时候老是提示参数不足，但是我在access查询这条语句是没有错误的。是怎么回事呢？
SQL code:
SELECT * from wcj WHERE Pno = '3' And TRim(Conclusion) = '合格' and (NET) is null

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SQL code:

SELECT * from wcj WHERE Pno = '3' And TRim(Conclusion) = '合格' and isnull(NET)


把你VB中的语句完整地贴出来
就是使用ADO或DAO访问的语句

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SQL code:

SELECT * from wcj WHERE Pno = '3' And Trim(Conclusion) = '合格' and [NET] is null

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VB code:
If Me.Check2.Value = 1 Then
If Me.Option1(3).Value = True Then
strSQL = " SELECT * from wcj WHERE Pno = '" & Trim(Me.TextPno.Text) & "' And TRim(Conclusion) = '合格' and [NET] is null "
Else
strSQL = " SELECT * from wcj WHERE Pno = '" & Me.TextPno.Text & "' and (NET) is null "
End If

Else
If Me.Option1(3).Value = True Then
strSQL = "SELECT * from wcj WHERE([testdate] BETWEEN '" &a