Form question: only allow iFrame embed in field by using pattern attribute

Hi there,

I would love to get some help with the following issue:
I’m building a member site where people can add embed soundcloud links to their profile. Although giving enough instructions to people they really should use the Embed code instead of just the http url, people are still adding an URL instead of embed code. To make this hufter proof, I would like to make sure the form can only be submitted if the field contains an iframe embed code. I have done this with other field where people need to fill in an URL, to make sure people add the http or https before the www., by adding a custom attribute: pattern = “http.*”, this works perfectly.
I was hoping to do the same for the embed/iframe field by adding the custom attribute "pattern = “<iframe.*”. But it doesn’t seem to work. Anyone has an idea how I can fix this?

I’m not familiar with how Soundcloud utilized their embed code, however is it possible for you to use dynamic embed fields instead? This would give users less information to include and should eliminate most issues.

Unfortunately not, as the embed code is to complex and has to many variations in different parts of the code, so I can not standardize the code and let the user only add one element. They would need to add the full code.