Checkbox and Consecuence

i am really new in programing so please be patient :)

I am working on a webpage for a local store, it is looking good right now but they ask me to add something i have no idea how.

They need 4 checkbox and a button:

Checkbox 1 Checkbox 2 Checkbox 3 Checkbox 4

Button

The idea is that dependding on wich checkbox are check the button will be one or another (i already have the buttons)

Example: if CHECKBOX1 is check then Show button A end if

if CHECKBOX1 and Checbox3 are check then Show button D

Why do they need this? They want a very simple "eshop" they have 3 products (A,B,C) each one with 4 options(1,2,3.4). and they work with a company "similar" to paypal that gives 1 button for each option the customer choose. (1 button for A1, another for A3, another for C4, Another for B.1.3, etc)

Can someone give me some help please? Thanks in advance