Question: Switching Video Sources.......

I currently have a Magnavox TP2792, and what i am trying to do is use my Time Warner Cable remote to switch between Video Input sources (dvd, cable box).  I have no manual for the tv.  I am able to access the menu and switch between sources, but what i am looking for is a faster way (ie. "one button press") with my TW remote.  I am able to do this on my newer TV without issue.  I feel that this Magnavox may be too old and not have that feature.  If anyone has any insight, any help would be appreciated.