Though we can use the default option in Wise Package Studio to add ENVIRONMENT VARIABLEs, sometimes we might need to add them using scripts. Scenarios like silent install need scripts to the job. I have created a script that I used for one of the application where i need to add custom value to HOME environment variable. My requirement is to add C:\VULCAN_TEMP value to HOME variable. If there is no variable then create. If there is a variable then append. During uninstall make sure the variable value is empty. 

Attached ZIP has install and uninstall Environment Variable scripts. Modify them according to your requirement.

Cheers!