vb424要求对象错误，怎么解决

Private Sub cmdClose_Click()
Unload Me
End Sub


Private Sub cmdFind_Click()
    Dim strSQL As String
    Dim strCno As String
    strCno = Trim(txtCno.Text)
    strSQL = "select Sno,Sname,Sdept,Sclass,Cno,Cname,grade from V_StudentCourseGrade where grade<60 and Cno='" + Trim(txtCno.Text) + "'"
    Call MsgBox(strSQL, vbOKOnly, "1")
    gradeADO.ConnectionString = getConnString
    gradeADO.RecordSource = strSQL
    gradeADO.Refresh

End Sub