How would i go about proposing appointment dates as a buttons to users

❓API

hey , i have made three form extensions taht should of capruters useer data to log into the crm once the use selects an avaialble timestamp form a button the ai privides on the date they selected one of the form extensions , how do i go about the ai checking google sheets and the date the user selected , then providing the open time stamps ive been stucj on this for 2 weeks now.