Originally Posted by
yanazake
Not sure if it's possible, but there may be a way of editing/saving some codes in the active sav file in the 3in1... Never used it, tho.
In the other hand, you can probably place the rom directly in the cart [by using gbaxploader. there are two options; quick load, and permanent load, where the rom is saved in the 3in1 memory until you replace it with another one or it runs out of energy for A LONG TIME] and place the cart in a gameshark device, since it works basically as a GBA cart when you place the game in it this way.
Hope this helped.