development of an employees leave record management system

my project goes like this i will have to make a development of an employees leave record management system for my subject for me to pass the graduation this coming march, that time i have to present a defense for my project, the problem i have to give you is this the first transaction is the employee will apply for a leave in the internet, the program will identify whether they are on vacation sick leave or in teacher's leave and then automatically compute for the remaining credit used and credit left, and that's all,please help me,so that i can finish my study,thank a lot, im waiting for the answer...and i have a favor that you can explained it to me on? how the system work and how am i going to defend for it, if i will be ask how i do it.