Using Ost and PST files

I have a two sets of calendars and contacts. one set syncs with my OST and the other I assume goes to my PST. By default if I select the contacts or calendar tabs those items will default to my PST file. I have to deliberately choose the other contact or calendar folders to have these new items go into my OST.

I am wondering how to make the calendar and contacts associated with my OST file be the default folders for these items.