Calculating the Deciles of a Group

[rprus003]

I'm trying to write in programming language a routine that will provide me with the deciles of a group of values and am encountering road blocks.

Example I'm looking at is:
- I have a dated workfile from 1980 to 2010.
- I have GDP per capita for 135 countries. Each series takes the form of "USA_GDPC"


What programming code would allow me to create a variables like "GLBL_10", "GLBL_20", etc which would be the deciles by year for all of the 135 countries?