vb连接SQL数据库

我用VB已经连接上数据库了,可是在连接以后打开另外的窗体的时候，报错

代码如下:
Private Sub Command1_Click()
Dim strSQL As String
Dim ADOrs As New Recordset
ADOrs.ActiveConnection = ADOcn

strSQL = "select * from stu_score"
strSQL = strSQL + " where 学号='" + Combo1.Text + "'"
strSQL = strSQL + "and 课程号='" + Combo2.Text + "'"
ADOrs.Open strSQL

If Not ADOrs.EOF Then
MsgBox "该记录已经存在，不能继续增加", vbCritical + vbOKOnly
Exit Sub
End If

strSQL = "insert into stu_score(学号,课程号,成绩)"
strSQL = strSQL + "values('" + Combo1.Text + "','"
strSQL = strSQL + Combo2.Text + "'," + Str(Val(Text3.Text)) + ")"

ADOcn.Execute strSQL
MsgBox "已成功添加新记录", vbQuestion + vbOKOnly

End Sub

Private Sub Form_Load()
Dim ADOrs As New Recordset