In your first example you could just call dopusrt twice, once to run each line. That avoids having to create a User Command and pass arguments to it.
If you do want to create a User Command then you can but it's very rarely used. Instructions on how to pass arguments to User Commands are in the manual under Predefined Commands / User - Predefined.
In your last example you've used @confirm incorrectly. It should always be on its own line.
You should also put quotes around the dopusrt path since it usually contains a space when %PROGRAMFILES% is expanded: