I'm annoyed

Because my agency phoned me today to ask me to be a forensic lab assistant on a crime show called 'Evidence' for Friday, Monday and regularly until the end of the season in March, and I can't do it because I'm working at UBC! I contemplated phoning in sick tomorrow, but in the end my better judgement prevailed. How annoying is that. Not only a regular appearance, but in a forensics series! I told the agent to snag me any further parts on the show, but I guess I just have to live with not being involved for now..... :o(