VB＋SQL　急急急！！！我急着要这个程序！谢谢

运行后显示：实时错误“3001”参数类型不正确，或不在可以接受的范围之内，或与其他参数冲突，我是新学的，所以请大家帮帮，谢谢了！

Private Sub Command1_Click()
Dim sql As String
Dim rs_add As New ADODB.Recordset
If Trim(Text1.Text) = "" Then
   MsgBox "用户名不能为空", vbOKOnly + vbExclamation, ""
   Exit Sub
   Text1.SetFocus
Else
   sql = "select * from 系统管理"
   rs_add.Open sql, conn, adOpenKeyset, adLockPessimistic
   While (rs_add.EOF = False)
        If Trim(rs_add.Fields(0)) = Trim(Text1.Text) Then
           MsgBox "已有这个用户", vbOKOnly + vbExclamation, ""
           Text1.SetFocus
           Text1.Text = ""
           Text2.Text = ""
           Text3.Text = ""
           Combo1.Text = ""
           Exit Sub
         Else
           rs_add.MoveNext
         End If
    Wend
     If Trim(Text2.Text) = "" Then
         MsgBox "密码不能为空，请重新输入！", vbOKOnly + vbExclamation, "警告"
         Text2.Text = ""
         Text2.SetFocus
         Exit Sub
    End If
   
    If Trim(Text2.Text) <> Trim(Text3.Text) Then
       MsgBox "两次密码不一致", vbOKOnly + vbExclamation, ""
       Text2.SetFocus
       Text2.Text = ""
       Text3.Text = ""
       Exit Sub
    ElseIf Trim(Combo1.Text) <> "system" And Trim(Combo1.Text) <> "guest" Then
       MsgBox "请选择正确的用户权限", vbOKOnly + vbExclamation, ""
       Combo1.SetFocus
       Combo1.Text = ""
       Exit Sub
    Else
       rs_add.AddNew
       rs_add.Fields(0) = Text1.Text
       rs_add.Fields(1) = Text2.Text
       rs_add.Fields(2) = Combo1.Text
       rs_add.Update
       rs_add.Close
       MsgBox "添加用户成功", vbOKOnly + vbExclamation, ""
       Unload Me
    End If
End If
End Sub