Changing source using variables in Power Query

Hello! I am trying to use a variable to replace 2 values at the end of a webcall I am making in power query in order to automate it for future use. My code is as follows:

let
LastMonthNumb = Date.Month(DateTime.LocalNow()) - 1,
CurrentYear = Date.Year(DateTime.LocalNow()),

PreviousMonth = if LastMonthNumb = 0 then LastMonthNumb = 12 else LastMonthNumb,
CorrectYear = if LastMonthNumb = 0 then CurrentYear - 1 else CurrentYear,

Source = Json.Document(Web.Contents("https://XXXXXXXX.XXXX/XXX/XXX/XXXXXX/2023/3")),

My goal is to put the variables CorrectYear in place of 2023 and PreviousMonth in place of 3 in my source. Any advice? Thank you!