How to prototype a dropdown menu effecting another dropdown menu

I created dropdown menus via components and variants for my prototype. The dropdown menu work great.

The user is able to select “Subscription” or “One-Time Purchase”
Here is the issue I am running into:

There are two dropdown menus.

1. Main dropdown: Subscription or One-Time Purchase
2. Sub dropdown: Subscription Options 1 month, 2 months, 4 months

If the user selects the “One-Time Purchase” option I am unable to have to automatically change the sub-dropdown menu to reflect the one-time purchase options (1 bag, 2 bags, 3 bags)