Create new record on dialog input

I've tried several variations of this (including a function) but so far nothing works.

I'd like to enter a customer number ("User card") in a number field ("Get a record"), and if the number exists popup the record (trigger on update.)

However, if the record does not exist I would like a dialog box to open asking to create a new record (yes/no).  If yes create a new record else open the "Main" table.

Here's what I've got that doesn't work:

let myInput := number(this.'Get a record');
let myRecord := first(select Users where 'User Card' = myInput);
let myRecordId := number(myRecord.Id);

if myRecord then
     popupRecord(record(Users,myRecordId))

else
    let result := dialog("User not Found", "Create new user?", ["Yes", "No"])
                  if result = "Yes" then
                         alert("Create record here")

                         else

                          alert("Open Start table")
                 end
      end

I've tried it with parenthesis around it, without, semi-colons, etc. and it won't do anything at all even if the customer number exists.

This works:

let myInput := number(this.'Get a record');
let myRecord := first(select Users where 'User Card' = myInput);
let myRecordId := number(myRecord.Id);

if myRecord then
     popupRecord(record(Users,myRecordId))

else

    alert("Here's an alert")

end

I'm not sure what the problem is or if there is an alternative to make it work.  Any advice is appreciated.