how can I upgrade iTunes without upgrading operating system

Hi all,

I'm using a mid 2010 Macbook pro 2.66 GHz, ICore i7, 4GB 1067 MHz running on OS X Yosemite. The Yosemite upgrade essentially rendered all the video I had imported into iMovie useless as I can no longer "preview" the video without converting it to Quicktime which takes forever. I don't want to upgrade again but I just upgraded my iPhone and it is telling me I have to upgrade iTunes. The App store only gives you the option to upgrade iTunes with the whole system upgrade. Is there a link or a way to just upgrade iTunes on it's own???