I only see this as a workaround. The real issue is why is the workflow asking for user input - they don't have to. There are two main ways to get a workflow to prompt a user - in the properties of the workflow itself (which will prompt the user for input before the workflow runs) and as a step in the workflow (which will prompt the user at some point while the workflow is running).
From your description it sound like the former - the workflow is prompting the user for some input at the beginning, before it runs. Wouldn't it be better to remove the prompting rather than use some technique to get around it?
Try editing the workflow. Don't click on a step (that will select that step - we want to stay on the worklow itself). Look at the Inputs tab and see what's there. Remove anything there.
Here is a screen grab of the inputs tab which shows how to add an input. Use this tab to identify and remove user inputs.
As for the second type of input (during the execution of the workflow) there is an easy way to turn them all off. Edit the workflow properties again (just like above) but this time go to the General tab. Look for the property Start Interactive Session. Make sure it's False. The workflow can't ask for user input if there is no interactive session. See here http://documentation.commvault.com/commvault/v11/article?p=49569.htm