Funnel dynamic RegEx

Question

I'm adding in a funnel for a specific journey to upload a photo via Facebook vs non Facebook vs YouTube etc. An example URL is below:

http://picturewall.mariecurie.org.uk/Upload/Step23/3631432911935?accessToken=CAAKeGTXwMDABAG7LSgs7YR7PTJ6ORSp2OhXUla85jr10UCOMNY9cTI2qVO8GaufA4p48bOYVcSexd0u50spJdOCYJXEUWZAhLZCu9ZAw52qU8Qyy3ZCO0MGotO0JXrkcDkZBzj5XE5ZA705KocaPQzCNR86ZBUDilzabfF37G7TC2usLFHT7uNJYgZBMc5DB9USPJi2OSdHHXGJz8W1nJfnq&PostType=Facebook – choose FB photo

What I want to do is to ensure that this step (choose Facebook photo) is tracked by picking up Step23 and PostType=Facebook as Step23 is used for other journeys where PostType=YouTube as an example.

I've suggested the below may work (with the view already filtered to just picturewall visitors): /Upload/Step23(.*?)(?!PostType=Facebook)

Is that the correct approach?