Kenobi from KodeWerx made an Action Replay DS hack that allows you to execute a custom ASM routine using the E type code. The only problem was that it would only for games without a custom "(M)" code. Here is a way I discovered to fix that problem.
Original E code type hack made by Kenobi
Replace 023FE074 with the address at line 7 in the custom "(M)" code.
Animal Crossing: Wild World (U 1.0) custom "(M)" code
023FF090 is the address that should replace 023FE074, giving you: 023FF090 012FFF11. To revert back to the normal E code type, you would use: 023FF090 E3520003. All credit for the codes should go to Kenobi; I just discovered a method for getting the hack to work with games that require a custom "(M)" code. I'm sure Kenobi could have figured this out himself if he already hasn't but, I didn't see any info on it.
00000000 023f0000 //Line 1
00000000 00000001 //Line 2
00000000 00000000 //Line 3
00000000 00000000 //Line 4
00000000 00000000 //Line 5
00000000 023ffe88 //Line 6
00000000 023ff090 //Line 7
00000000 00000000 //Line 8
00000000 00000001 //Line 9