So, this is the whole AppleScript that worked for me, to set the new event and open it in Calendar.
Thanks so much again, @Jim and @ccstone
set theDate to short date string of (current date)
tell application (path to frontmost application as Unicode text)
set varCal to (choose from list {"Family", "Work"} with title "List of Calendars" with prompt "Please select a calendar" default items "Family" OK button name {"Choose"}) as string
end tell
display dialog "Enter the date:" default answer (theDate as text)
set varDate to text returned of the result
set varTime to (choose from list {"09:00", "09:30", "10:00", "10:30", "11:00", "11:30", "12:00", "12:30", "13:00", "13:30", "14:00", "14:30", "15:00", "15:30", "16:00", "16:30", "17:00", "17:30", "18:00", "18:30", "19:00", "19:30", "20:00", "20:30", "21:00", "21:30", "22:00", "22:30", "23:00", "23:30"} with title "List of start times" with prompt "Please select the start time" default items "11:00" OK button name {"Choose"}) as string
set varStart to date (varDate & space & varTime)
set varEnd to (date (varDate & space & varTime)) + (1 * hours)
display dialog "Enter the event:" default answer "Appointment with "
set varName to text returned of the result
display dialog "Enter the description:" default answer "→ "
set varDesc to text returned of the result
set varLocation to (choose from list {"Home", "Work", "Other"} with title "List of locations" with prompt "Please select a location" default items "Home" OK button name {"Choose"}) as string
tell application "Safari"
set varURL to URL of front document
end tell
display dialog "Enter a link:" default answer varURL
set varURL to text returned of the result
set varRemind to (choose from list {"0", "-15", "-30", "-60", "-120", "-1440", "-10080"} with title "List of reminder miutes" with prompt "Please select a reminder time" default items "0" OK button name {"Choose"}) as string
tell application "Calendar"
activate
set theCurrentDate to current date
set newEvent to make new event in calendar varCal at end with properties {description:varDesc, summary:varName, location:varLocation, start date:varStart, end date:varEnd, url:varURL}
tell newEvent
make sound alarm at end of sound alarms with properties {trigger interval:varRemind, sound name:"Crystal"}
end tell
show newEvent
end tell