erm.. i don't really know what to tell you otehr then it's YOUR job... it's not school... you can call in and say "i don't feel like coming in today, i've got the serious shits and this dude just showed up with an 8-ball..." and there's not really anything they can do short of firing you (with school you'd face legal complications)....

if i wanted off that bad, (depending on the job) i'd just tell them i'm taking hte day off.... i see people (through my wife's work, and when i worked at sonic, and johnny carinos) telling the bosses all the time they're taking hte day off.... the boss wasn't happy, but i never see anyoen get fired for it.... bosses have other ways of retaliation... giving you the shittiest assignments, hardassing you (breathing down your neck), shorting your hours... etc etc.... firing isn't the only thing bosses do to workers they're not happy with ya know...