You do need two programmed keys to do a "customer spare programming" but there is more than one way to skin this particular cat.
You can program an additional key with the scan tool, that does not require two programmed keys.
You can get a second key cut (and really, that isn't a bad idea).
Also, which vehicle do you only have 1 key for? The Ranger, The Explorer, or both? If you have two for the Ranger there should be no problems about two keys.