I am pretty sure I have seen both terms used together, though it was some time ago and I can't remember where it was. I am fairly sure it was in a Latin American document, possibly from Mexico.

The question of which country it is may well be significant. I don't think this distinction is made in Spain. But in some Latin American countries it is. The explanation that follows relates to Peru, but it probably applies to other countries too.

The "orden del día" is just part of the "agenda". The latter is what we would call the agenda in English: a list of the items of business to be conducted at the meeting. But "orden del día" specifically means what we would call in English the matters for discussion; it does not include what we call matters for report.

The order of business at a meeting in Peru is as follows:
"Estaciones o momentos de la sesión"
- Control de asistencia: check to make sure there's a quorum.
- Despacho: chair asks secretary to read correspondence received since last meeting. NB: "Los documentos que necesitan ser debatidos pasan a "orden del día".
- Informes: members report on business they have conducted since the last meeting, starting with the chair. NB. "El informe que requiere debate pasa a "orden del día".
No debate is allowed during these stages (Despacho and Informes). Together, they constitute what we would call "announcements by the chair" and "matters for report" (the latter usually comes later in English-speaking countries).
- Lectura de la agenda: the chair reads the agenda, which has been prepared and distributed in advance.
- Pedidos: at this point members can propose items for inclusion in the agenda, for subsequent discussion.
- Orden del día: the main part of the meeting: presentation and discussion of agenda items, including those matters for report (items from "despachos" and "informes") which have been added to the matters for discussion.
- Tratamiento de pedidos: the meeting decides whether to debate the "pedidos" raised earlier.
- Aprobación del acta: approval of the minutes which have been written up while the meeting was going on.

The above is a summary of the section on "Acta" from here:
http://www.monografias.com/trabajos43/documentos-administrat...

Having been secretary and minute-taker of a meeting in my time, I can attest that the above is really quite similar in broad terms to the way we do things, though the order is different (and we approve the minutes at the beginning of the following meeting).

I think the distinction it involves between "agenda" and "orden del día" is almost certainly the one that applies in your case, and that you can translate them as "agenda" and "matters for discussion" respectively.

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Note added at 4 hrs (2013-06-13 08:29:19 GMT)
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The following, from a Peruvian university, confirms that the above is how it's done in that country:
"Art. 3º Las sesiones ordinarias comprenden las siguientes secciones:
1. Lectura del acta anterior y aprobación de la misma.
2. Despacho
3. Informe
4. Pedido
5. Orden del Día
El desarrollo de la sesión respetará el orden anteriormente establecido. [...]
Art. 13º En la sección orden del día se empezará discutiendo los asuntos consignados en el Despacho, y luego los informes y pedidos, en estricto orden de recepción."
http://www.unp.edu.pe/noticias/reglamentosesionesconsejouniv...