Lookup function for a Roster

Hi

I'm new to excel and having a problem with a "lookup" formula.

I have 4 Teams with 2 employees per team. When an employee applies for annual leave, details are added in the "Leave" sheet.

My aim is when I put the leave in "Leave" sheet, I like it to automatically place in the month tab "April" on the bottom to indicate the employee is away for those days. Maybe Have an "Leave" text in boxes.

If anyone knows of a formula or a way I could accomplish this I would be very greatfull. I have a basic/intermediate knowledge of excel so if it could be explained in idiot format, it would be apprecitated. Thank you in advanced.