Create Excel Spread sheet

Create an excel spreadsheet that allows us to enter in a list of specific details from each of our real estate transactions. Have multi tabs for different agents the auto calculate and combins data entered onto page 1 so we can view totals and specific metrics we need to monitor all our transactions. Need to have the ability to handle 500+ transactions on one page and auto calculate info and combine data from all tabs. I dont want to have limited ability to add more transactions and have to adjust the formulas ourselves. The spread sheet eeds to be scalable to handle a high number of transactions. Have the ability to add, edit and remove agent names to drop down menu on the main spreadsheet page. When we add a name a column should auto matically add to the other tabs of the spread sheet where it will then auto calculate the total number of transactions of that agent.