Get Info Command fails to keep settings

On my machine I have two versions of Excel (Excel X for Mac and 2011). I installed the latest version so that I could access some of the new features in Word that are not in the old version. However, I wanted the majority of my Excel files to open with the old version. However, when I use the Get Info command on an individual file which allows me to choose the opening application it seems to lose the settings upon closure. Even with the old version selected if all apps are closed and that file is opened it will open with the new version. If the old version is running, then no problem the Excel file opens in that version - but it always defaults to the new version if both apps are closed. This means that before opening a file you have to launch the app version you need. Frustrating. Is there a work around for this? Needless to say the Change All option of having all files open with the old version is equally inoperative.