Essbase substitution variables are global placeholders for data whose values can be set for the entire Essbase server, an application or database. The following technical note explains how to create substitution variables in Essbase and how to use them in MDX reports:
KB47150: How to use Essbase substitution variables in MDX reports in MicroStrategy Desktop 9.x
The below steps describe how to use Essbase substitution variables in report filters within an MDX multisource report. In this example, a substitution variable 'CurQtr' was created in Essbase so that it would be replaced with the value of the current quarter (which in this example is Qtr1) when it is passed to Essbase. Furthermore, the 'Year' attribute from Essbase has been mapped to the project attribute called 'Year':

KB47602