Travel visa extension? (Barcelona)

Hello all,

I am Matthew Hughes, 22 years old from New York and living in Barcelona while I pursue my masters degree in Medieval Cultures at the University of Barcelona. My decision to apply to the UB was made very last minute (about mid July) and by the time that I had received notice of my acceptance, the faculty and staff had gone on vacation for the month of August. This was a problem because I needed a certain document from the UB in order to complete my student visa process. I came to Barcelona at the end of August in order to attend the Catalan courses offered by the university. So, the plan was to have my parents complete the visa process for me and then I would have to fly home, retrieve the visa, and then come back here. My question is, can I have my travel visa extended until I have a long break in classes so that I can go home then and retrieve my visa without having to miss any of my classes? Thanks for any help, I really appreciate it.