Apt-Get Upgrade One Repository Only

I have a few mashines running on debian system with added my own packages repository. I want to set auto system packages upgrade, but only from my repository. I don't want to automatically upgrade official packages - only if needed by mine packages.

I have tried to change priority in /etc/apt/preferences. I can block there official repositories from upgrade, but it will also block upgrade when any of my packages will depend on any official packages (needed to upgrade or install).

Is there any simple solution to upgrade only packages from one repository and get packages from another only when needed?