Hi Stephan, welcome to the forum!
When you make a file trigger, you should know the path where the files will come in.
As the filename for the trigger you could use 'Trigger*.txt'. The * lets trigger the job on evet file that starts with Trigger and ends with .txt.
You should know that this filename also will trigger the job: TriggerFinger.txt The * lets everything pass.
If you want to be sure the triggered file ahs a pattern, you could make a condition.
This condition checks the filename of the trigger to a format you want (string compare) with the todays date.
You add this condition to the 1st task in your job.
In the actions of your condition you tell the jobs to stop when there is no match and to continue if there is a match.
Good luck!
Regards
Erik
Uses Visualcron since 2006.