mariu5, por favor, dê uma olhada em Como mostrar um resultado de fórmula em uma legenda do gráfico do Excel , HTH. O ponto é, você precisa criar primeiro as fórmulas nas células da tabela, então você pode fazer referência a elas!
Here is one way of making your legend follow the years in row 1 and the averages in row 14.
First of all, create this formula in a blank cell, eg. A17:
=TEXT(B1,"0000")&" - Average "&TEXT(B14,"0.00")
Then create this formula in say A18:
=TEXT(C1,"0000")&" - Average "&TEXT(C14,"0.00")
These two formulae generate the legend you want to achieve, making use of the TEXT function to determine the formatting of the numbers involved.
Now go to your chart and choose the Source Data command from the Chart menu. In the Source Data dialog box, make sure the Series tab is selected.
Select the first series in the Series list. Click the Collapse Dialog button to the right of the Name box. Click on cell A17 in the worksheet. Click the Collapse Dialog button again to return to the Source Data dialog box. Repeat the process for your second series and you should have a legend that looks like this: