URL without for attribute “http” not opening correctly

Hi,

I included an attribute #_ATT{Homepage} on my events-manager. Guests can insert an URL which will show up within the event details.

The problem is, when the guest enters an URL like this: http://www.guestwebsite.com (without the “http”) the Link will not open correctly. The system then makes this Link: https://mywebsite/event-manager/www.guestwebsite.com which of course leads to an 404-error.

How can I fix it, that the link http://www.guestwebsite.com will automatically turns into http://www.guestwebsite.com or opens without putting my website address in front?

Im looking forward to a solution. Because right now, I habe to correct all these links manually.

Thank you.
Sabo