Updating recent data

I have an Excel file that my assistant uses to check bi-annual sales data. Every six months new data is put into columns and tables and graphs are made from the updated data. I have built it so the data entry is on one tab and the formulas for calculating averages and what not are on another tab. I have it set up so that each column represents a six month period and the rows represent the sales persons. I was wondering (1)if there was anyway to have the formulas adjust when data is put in and (2) if there was a way to have the graphs update with the new data. Thanks.