Yes it can.

This
 Code:
Set "Test=TestEnvVar"

will set the environment variable Test to TestEnvVar.

This
 Code:
Set "Test="

will remove the test environment variable.

Please note that you may need to start a new instance of an app if it was running while you did the change.
For example cmd.exe will not show the changes if it was running when you did the change. If you restart cmd.exe all changes are visible. The SET command will set the environment variables for the current user. The SETM command will do just the same as the SET command does but for the local system. SETM requires admin privileges for the user running the script.
_________________________
Mart

- Chuck Norris once sold ebay to ebay on ebay.