Creating calculated columns that ranks table by numeric column

Hi

I am trying to add 3 calculated columns that will rank every row by column D (Sales) . I have used the RANX function but could not manage to do it.

1. The first calculated column ( Column E) should be done for the whole table and rank every row by the Sales column
2. The second calculated column (Column F) should do it over Position column by Sales Column
3. And the last one ( Column G) should to it by Region and then Position  

Many thanks in advance