[power-pro] How to set environment variables that expand in path statements?

[i_karaguz]

I'd like to set an environment variable and later refer to it in a
path  statement.

Just like "%programfiles&\foo", where 'programfiles' is e.g. 'myvar'.

Invoking Exec.SetEnv("myvar", ?"c:\test") and typing %myvar% in
Start->Run doesn't work.

Is there a way to do this in PowerPro?

Thank you!