IMO the best way to translate this is by "intensive seminar". It basically means that several days are "blocked" (in your diary as it were) in which the seminar takes place.

I saw this for example when doing my MBA. All modules were 21 hours long, and we normally had 3-hour classes, but for one particular module the lecturer came from abroad and we had two full days "blocked" in which we studied that particular module.

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Note added at 42 mins (2011-10-25 05:46:38 GMT)
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"Le deuxième se déroule en séminaire bloqué et de manière continue (semaines complètes dédiées à l’activité) et est à caractère informatique et marketing."
http://iteem.ec-lille.fr/entreprise/stages-et-projets/les-pr...

"Programme proposé en Part Time sur 12 mois (cours les vendredis et samedis, 2 à 3 fois par mois en moyenne, avec une semaine de séminaire bloqué du 20 au 24 février 2012)."
http://www.mba-iscparis.com/mba-part-time/master-marketing/m...

Welcome to the Intensive Seminar Extranet!
The Intensive Seminar on the European Union is a one-, two- or three-week training programme providing professionals with in-depth knowledge and practical skills on EU decision-making and policies.
http://is2008.coleurope.eu/