Update a path Environment variable

[yannos]

I would like to add a path to the path environment variable "path". But I don't know how to do it.
I use Installshield 2013 and an installscript project.
I've seen we can defined path variable environement on "Media|Path variable" .
But how can I change the path?
Thanks for your help,
Yann

[TsungH]

Here is one way.