Percentage of one level up

One of the most common calculations is calculating the percentage of the current value to the total one level up. For instance [Measures].[Sales Amount] for the quarter compared to the semester.
This gives use several challenge's.
1. What is the total amount one level up. With the .CurrentMember property we know where we are. If we combine this with the .Parent property we can calculate the total amount: ([Measures].[Sales Amount],[Date].[Calendar].CurrentMember.Parent) .

Ancestor

The Ancestor functionality allows us to find, parents, grand parents, great grand parents etc.… The number of levels you want to go up can be a number or a dedicated level.
The Ancestor with a level of 1 is the same as the .Parent functionality
Let’s try:

Parent, FirstChild and LastChild

Using the Parent functionality you can get the First Child and Last Child within hierarchy level. 15-JAN-2011 ==> Parent = JAN-2011 ==> FirstChild = 1-JAN-2011 ==> LastChild = 31-JAN-2011.
Here is an example: