Power query from web.content with variable parameters (in query itself)

Hello,

I may be looking for the solution using wrong naming, but I didn't find what I a looking for

Basicaly, I have a power query (using web API) where I wish to have some variable in the query itself

let
Source = Web.Page(Web.Contents("https://thesite.com/API/Server?date=[-1,-1]&apiid=variableparmeter1&account=[Cust-03]&metric=[client_id,date,CustInfo1,CustInfo2]&frequency=day&format=html&sortby=[client_id,date]")),
Data0 = Source{0}[Data],
#"Changed Type" = Table.TransformColumnTypes(Data0,{{"client_id", type text}, {"date", type text}, {"CustInfo1", type text}, {"CustInfo2", type text}})
in
#"Changed Type"

I would like in the sheet itself having:

1) a fixed "password like" which I could change anytime (and use running "refresh the query")

2) (I guess that answering 1 would answer here too) A data validation from list, where I could select one customer and then "refresh the query" using the selected customer

Customer list

Thank you in advance for your help (may be redirecting me in an existing topic)