how am i going to tell my boss??

on mon
boss: thurs we go outstation a.. i go pick u
chyeli: outstation a? ok.. (thought one @ 2 days only de..)
boss: we will go on thurs, fri, sat, sun, mon and tues.. tues we come back
chyeli: (shock.. cause have accounting night in genting this weekend) cannot a boss.. sat n sun uni got activities
boss: then cannot go liao lo
chyeli: (checking schedule..) next weekend shouldn be a prob.. next thurs
boss: (checking calendar..) then next weekend only we go la..
chyeli: (relief.. but hav to forgo my accounting dinner on the 27th)


on tues
ling: softskill presentation going to be on the 27th 9am..
chyeli: wat? 27th? but i am going outstation wo
ling: huh? must acknowledge the boss.. cause u know this have to attend de la.. if not cannot graduate
chyeli: dying this time.. i just tell boss i cannot make it this week and next week shouldn be a prob

i didn know how should i tell my boss this time.. and i bet tomolo i need to tell him already.. please.. hope he won angry at me.. hope i could make it in april cause i hav appointment regard school already.. =( boss a boss.. dun angry at me a..