You need at least 2 keys before you can program another in, yourself, on a 99+.
You can try calling local locksmiths and repair shops, some will have an NGS and will do it cheaper than ford.
2007 Shelby GT500 705RWHP/708RWTQ
2000 Mustang 3.8 A4 TT 450RWHP/475RWTQ 10.996@127 17psi stock 3.8
2006 F250 CC 4x4 6.0L 14.3 @ 93
2006 Mustang 4.0 M5 Vortech 13psi 395RWHP/374RWTQ wife's car