Loop the Workflow
The next step in the workflow is to activate the screen saver after the image has been taken.
Select the System action group from the Library list and drag the Start Screen Saver action from the Action list to the end of the workflow.
And the final step in the workflow is to have it repeat automatically so that the naming dialog will always be available to start the process of taking another snapshot. To accomplish this, you'll use the new Loop action in Automator.
Select the Utilities action group from the Library list and drag the Loop action from the Action list to the end of the workflow.
The Loop action will cause the workflow to be executed again from the beginning, following the parameters you select in its Action View. Set the workflow to loop automatically, using the original input, for 240 minutes (4 hours). Of course, you can set the loop duration to be a specific number of times as well.
You've now completed constructing the workflow and are now ready to save it.