If your organization uses an install creation program such as InstallShield or Wise, you might already be creating Microsoft Installer major upgrades, minor upgrades and patch files for your software. If this is the case, you can utilize the Execute Msi update action to launch your upgrade or patch during an update. You can define the exact command line parameters to pass into the msiexec.exe. When the package is downloaded, verified and executed, your patch will be automatically executed on the client computer.
Note: Microsoft Install Patches cannot be created directly within a Visual Studio Setup Project. You can create an installer patch using the Microsoft Installer SDK. More information can be found at http://msdn2.microsoft.com/en-us/library/aa372866.aspx