Updating database & Chart

I get a chart like the one attached every month. It shows the acceptable and unacceptable sales calls for each employee, as well as the previous accumulated totals, and the new totals that add (or subtract) the current month.

It also gives the supervisor and department for each employee.

I need to update a chart each month that shows 2 things:

1) The net activity (acceptable minus unacceptable) for the month for each Department (not employee). Unfortunately, each department gets listed in two different places, and I need to sum those (I have no need to show them separately)

2) the combined net activity (acceptable minus unacceptable), which totals all employees and departments into 1 figure.

I have to update these 2 charts every month, meaning I have to add a new data point to the graph and connect it to the already existing graph that had been created for all the previous months.

I get this report each month as an additional tab in an already existing worksheet that has all the previous months in their own individual tabs.

Can anyone help me automate this effort, or at least provide some advice on the easiest way to accomplish this.

Thanks in advance.

Thanks Andy, that works really well. Now I just need to find out how to take those totals and add them to an already existing graph.

For instance, I have a chart that has Jan thru Oct totals for East Coast. Now I need to add the Nov total to that chart.

I need to do the same for West Coast.

Any ideas on the easiest way to do that? Can I record a macro that will do it or something like that? I'm wanting an idea that requires the least amount of effort because these reports have to be updated monthly and there are about 500 of them.

thanks again for your help!