Dex Number Offsets and Format
Haven't tried your editor yet, but I've got a project of my own I'm working on, so I know how all the dex numbering works for FR/LG/R/S/E. This should be all the info you need, at least for the English versions of the games. (I'm giving more details in case anyone else reading the thread is interested.)
Dex numbers are stored at 2 different offsets: 1 for national number, 1 for Hoenn number. In both cases they consist of a sequence of 411 (or 412 if you count Pokemon #0) 2-byte, little-endian integers where each integer represents the dex number for the Pokémon at that location. They are ordered by the in-game Pokémon number.
For the national dex, starting with Bulbasaur = #1 you would have the bytes:
0x01 0x00 0x02 0x00 0x03 0x00 ...
And for the Hoenn dex, starting with Bulbasaur = #203 you would have:
0xcb 0x00 0xcc 0x00 0xcd 0x00 ...
I'm giving offsets beginning with Bulbasaur here. If you want to include Pokémon #0, just decrease each offset by 2.
# Leaf Green
[BPGE]
DexNumbersOffset = 0x251fca
HoennNumbersOffset = 0x251c94
# Fire Red
[BPRE]
DexNumbersOffset = 0x251fee
HoennNumbersOffset = 0x251cb8
# Ruby
[AXVE]
DexNumbersOffset = 0x1fc516
HoennNumbersOffset = 0x1fc1e0
# Sapphire
[AXPE]
DexNumbersOffset = 0x1fc4a6
HoennNumbersOffset = 0x1fc170
# Emerald
[BPEE]
DexNumbersOffset = 0x31dc82
HoennNumbersOffset = 0x31d94c
One thing to note (not sure if you plan to take care of it in your program or not) is that while you can change the national and hoenn numbers by modifying the data at these offsets, the Pokédex entry is tied to the national dex number, NOT to the Pokémon. So, if you just went to the dex numbers list in say emerald, and swapped bulbasaur's and charmander's numbers, charmander would now be #1 in the dex; and it would now have the height, weight, and description of dex entry 1 (previously bulbasaur).
Hope that helps,
-Silver314
