Enviroment variable in .desktop

[Qihua Wang <qihua wang alcatel com>]

Is there any way to put in text in the xxx.desktop for Exec= that would pick up, not the literal text, but a value from 
elsewhere? Like an environment variable?
I'd like to have the launch location specified in .desktop using environment variable since I don't know where the user 
installs the application for launcher.

Thanks!

-Qihua