Delphi and Text input

[drama22]

hi, regarding my previews post iam trying to submit youtube links to other form i done with every thing but one thing has left ,, i want to allow only youtube links to be sent like only youtube links can be submitted i try method to force the text input to have more than 33 chars like this

Delphi-Quellcode:

begin
  if Length(Trim(Textinput.Text)) < 33 then
  begin
Application.MessageBox('Thats not youtube link', 'Info!', mb_iconWarning);
  end

basically this well force to insert text longer than 33 length but thats not the goal ,, is there any function to check if there is youtube url or not ?