There are a couple of things that you need to consider in a task such as this:
a) what sort of output do you require? b) how are you going to manage the data?
For a) I'd separate it further into the basics of what's required (time series charts of employee and/or team performances [how will team performance be measured? average, % achieving 4, or ?]) and then the bells and whistles of drop-downs. Focus on the basics, the other stuff first the whizzy stuff can come later. Getting b) right is vital - you are going to be extracting subsets of the data to build the charts you want to display. Get b) wrong and you'll just create a horrible task for yourself.
In your position I would consider re-organising the data into the form of a table. Excel's help defines what is meant by a table, but in essence it is a list of your observations where each observation simply comprises the score for a particular month/team/employee/task combination (so each observation comprises 5 values). The observations are arranged as successive rows of the table with the first row being the header row which will contain suitable labels such as "Month", "Team", "Employee", "Task", "Score". The real advantage of using a table such as this is that Excel provides a heap of in-built facilities for manipulating them - look up the help for Sort and Filter on the Data tab. In your case there is an even more compelling reason for using a table - you can use the Pivot Table and Pivot Chart facilities for analysing and displaying the data. If you have not used these before some time and effort spent learning about them will pay dividends. Once your data is organised and you know how to use Pivot Tables and Charts you should be able to prototype sum output very quickly.
If you do decide to organise your data as a table you can still keep a nice friendly looking grid of 6 team "tables" (different from Excel's use of the word) as a data entry facility to enter each month's scores by employee and task. You will need to find a way of getting each month's data from the data entry "tables" to the main data table. (Easiest way would be to use a bit of spare worksheet under the data entry tables to reproduce the entered data as a series of observation rows and then use Paste Special Values to append these rows to the end of the main table of observations. You can use VBA to automate the copy/paste operation if you want, you just need to figure out a way of identifying how may observations are currently in the main table and precisely where you want the paste to end up - COUNT() or COUNTA() is a useful friend here). Main problem to avoid (whether automated or not) is to avoid appending same entered data more than once to main data table.
Have a look at http://www.mediafire.com/download/x64swkp689k10a1/DataEntrytoTable.xlsx for a simple example of some of the above thoughts