Utilization of Blogs in the Spanish Classroom

My initial intent for participating in this workshop was to eliminate the weekly journals that I require for my second year and advanced students. Each week 75+ students are required to write five sentences in Spanish in the topic of their choice, one which must focus on the grammar topic of the text during that week. I dutifully haul these journals home every weekend, spend two hours reading and correcting, indicating errors that should be corrected. If the student hands the journal in on time, the grade is an automatic C, with the possibility of the A when the errors are corrected and resubmitted with the next journal entry. I firmly believe that each student is able to improve his or her writing skills at the individual proficiency level of that student with this system.
I would like to use technology as an alternative to the physical journals. Blogging would provide an audience, but how would I be able to indicate the corrections? I fully know that some educators subscribe to the theory that students should be allowed to write in a stream of consciousness style and should not be stifled by corrections. However, I believe that an important objective of the class is to improve written proficiency, and that I would be doing a disservice to my students by not requiring corrections. Since I will be teaching a full schedule of 150 students, this is one of the few formal writing requirements that I utilize, and former students presently at the university level insist that it prepared them for much more demanding writing at the college level.
I may just begin with the 34 advanced students, but I will have to devise a system for corrections and improvements and would welcome a solution.
Kathy