Brilliant Diamond v.1.1.1 / Shining Pearl v.1.1.1
Replace the X's with the numbers for the multiplier you want
[Brilliant Diamond EXP Multiplier]
040A0000 0206A738 0B1
XXXXX
[Shining Pearl EXP Multiplier]
040A0000 0240DAD8 0B1
XXXXX
50138 = x1 (aka normal exp)
50538 = x2
50938 = x4
50D38 = x8
51138 = x16
51538 = x32
51938 = x64
51D38 = x128
52138 = x256
As pointed out in an earlier post, the EXP received won't show as modified when you defeat/capture a Pokemon but it does give you the full amount if you look at your Pokemon's summary sheet after the battle.
Still trying to find a way to receive 0 or close to 0 exp, if anyone finds the code, please share