How to replace variables cross form

I am currently working on a video game project,

And have 3 forms.

Room1, Room2, and Battle forms.

My question is, is there a way to pass variables(like you would to a method) so that it replaces the ones already being used

for example, you are in Room1 and get in a battle.

then in Room2 you get in a different battle, so i would need to pass a different set or variables for the different monster.

How is this possible to do?