I think you can check the software distribution properties, with MSI packages, you can specify if you want to see the progress bar or if you want to do a silent install or in you command switches.
You can change the delivery method to hide all the feedback.
Go into the Delivery Mehtod used (I'm guessing you're using the policy "Always listed for installation".
On "Feedback and Timing" change Package Progress UI to "Hide all feedback from user".
cplatero has the correct info