求教登录界面同时区分大小写

    If rs.EOF = True Then  '如果没有记录则说明用户或密码为错误的
        If pnum < 2 Then 'pnum就是密码验证次数，当次数超过3次，系统会自动保护退出
            pnum = pnum + 1
            MsgBox "用户名或密码错误!（区分大小写）", vbInformation, "错误次数：" & pnum
            rs.Close
            cn.Close
            Text1.Text = ""
            Text2.Text = ""
            Text1.SetFocus
            Exit Sub
        Else
            MsgBox "用户名或密码错误超过三次,系统自动退出...", vbInformation, "提示"
            End
        End If
    Else
        loginname = rs.Fields(0)
        Form3.Show
        rs.Close
        cn.Close
    End If