主题：[求助]想做一个筛选窗口，认为未填写内容的单元格都符合筛选条件，请问如何实现？

or 条件，要加上括号

DataTables("b1").Save()
Dim Filter1 As String
With e.Form.Controls("TextBox1")
    If .Value IsNot Nothing Then
        Filter1 = "(a1 <= '" & .Value & "' or a1 is null)"
    End If
End With
With e.Form.Controls("TextBox1")
    If .Value IsNot Nothing Then
        If Filter1 >"" Then
            Filter1 = Filter1 & " And "
        End If
        Filter1 = Filter1 & "(a21 >= '" & .Value & "' or a21 is null)"
    End If
End With
With e.Form.Controls("TextBox2")
    If .Value IsNot Nothing Then
        If Filter1 >"" Then
            Filter1 = Filter1 & " And "
        End If
        Filter1 = Filter1 & "(a11 >= '" & .Value & "' or a11 is null)"
    End If
End With
With e.Form.Controls("ComboBox6")
    If .Value IsNot Nothing Then
        If Filter1 >"" Then
            Filter1 = Filter1 & " And "
        End If
        Filter1 = Filter1 & "(a17 like '%" & .Value & "%' or a17 is null)"
    End If
End With
If Filter1 > "" Then
    Tables("a1").Filter = Filter1
End If