Different code behind “Sign up with Apple” and “Continue with Apple”?

Do you know if we can code a “Sign up with Apple” button differently to a “Continue with Apple” button?

The reason I need to know this is because I want to have users select the 'Sign up with Apple' button when they are on the sign-up screen and the 'Continue with Apple' button when they are on the log in screen.

This will stop users that already have an account with my app, creating unwanted multiple accounts when only being able to sign up with Apple.

thank you