Excel 2007 : Using data tables and IF functions

I was asked to do the following:

Starting in cell I5, enter the values -5% to 10%, incrementing by 1. Use the values to create a list box in cell C13 with the input message select the assumed percentage change from the current year's sales from the drop-down list and the error message You must select one of the values in the drop-drown list box.

Can someone takes me into the right direction as to how to start please?

Thanks!