help with run

I am making a reverse mario game. Instead of you being mario, you are a goomba. I want to have it so when i hold shift and walk i will sprint. Right now the speed is 4 and -4 and i want to have it when i hold shirft and walk it will be 6 and -6. @grazer plz help. Or anyone.

oops i just relised i put shirft not shift.