This can be accomplished using the apt-pinning feature. A typical use case is prioritizing local packages over remote ones or installing older package rather than the new ( unstable ) one in other repository.
Just create a file ‘preferences’ in the ‘/etc/apt/’ directory.
$gksudo gedit /etc/apt/preferences
Then add the packages required ::
Pin: origin *
The default priority is 500, anything greater will be prioritized.
For eg, if you want to install package ‘skype’ from the ‘medibuntu’ repository add the following ::
Pin: origin packages.medibuntu.com
More info can be found here.