Luckily, I was able to get this working through trail and error.

Step 1: Log in to the Plesk admin area and click on the domain you want to run the scheduled task for. Click on the icon for scheduled tasks.

Step 2: Add a new task. You’ll need to make sure php-cgi is enabled for your domain as well.  For the “path to executable file” you’ll put:  “c:\program files\path to plesk\php-cgi.exe”.
The argument will be the full path to your php file you would like to run. It might look something like this: “c:\inetpub\vhosts\mydomain\httpdocs\cron\mytask.php”.

Pick a time for your task to run and let the WIN roll in!