Private Sub Combo4_Change()
    If Trim(Combo4.Text) = "" Then
        List1.Clear
        List1.Visible = False
        Exit Sub
    End If
    If bbb = True Then
        List1.Clear
        List1.Visible = False
        Dim mrc As ADODB.Recordset
        txtsql = "select   DISTINCT 姓名 from xj where 学号 ='" & Trim(Combo4.Text) & "'"
        Set mrc = ExecuteSQL(txtsql)
        If mrc.EOF = True Then
            sss = MsgBox("没有此学号！", vbExclamation + vbOKOnly, "警告")
            Text2.Text = ""
            Exit Sub
        End If
        Text2.Text = mrc.Fields(0)
        Set mrc = Nothing

        Exit Sub
    End If
    Dim rst As ADODB.Recordset
    Dim str As String
    str = "select 学号 from xj where 学号 like'" & Trim(Combo4.Text) & "%' and 班级='" & Trim(Combo2.Text) & "' order by 学号"
    Set rst = ExecuteSQL(str)
    If rst.EOF = True Then
        List1.Clear
        List1.Visible = False
        Set rst = Nothing
        Exit Sub
    End If
    List1.Clear
    Do Until rst.EOF
        List1.AddItem rst.Fields(0)
        rst.MoveNext
    Loop
    Set rst = Nothing
    List1.Visible = True
End Sub
这里的bbb是什么意思，bbb在通用声明定义Public bbb As Boolean，这里bbb的作用我不太明白，它代表的是什么意思啊

哦，好的 我看看下，待会有问题再问你，谢谢你最近都帮我啊