How to make my cough worse?!

i need to get out of goin to my grandmas, and the only way i can stay home is if my cough gets worse, becuase i get bronchitis so much. 2 to 3 times a year. and my cough is farely bad, i dont want to become sick, i jsut need to get a littlw bit worse, the reason i dont wanna go to my grandmas is couse i need to stay home and study for a test that im not prepared for at all. its monday. my parents wont let me stay home , unless sick. even if i tell um i need to study they say, well you had other times to study. thanks a lot. and i understand thats its my fault i didnt study. but wed be leaving saturday after noon, and we wouldnt get back til late sunday. so i just need my cough to sound barking, and really bad, becuase it sounds like that, but then if i try to fake it, its like eh eh, instead of cuh cuh cuh cuh