Java notify when source is updated

So basicly the problem is: I have 2 cells in a sheet in a java program (kind of a excel like program) and i want to make a method that will repeat itself everytime this cells are updated. More specifically every time a user changes the cells on the sheet i have to repeat a method that will import the information of the cells to a list. So i will need to repeat this method automatically x times, depending on the cells behavior. Any ideias how to do this? Thanks