Form / Field Validation on a button...?

Hi

I have a form where I want to replace the Submit Button with a regular button to take better control of the created email title and body etc. I think I can achieve this using knowledge from previous threads on here however I am struggling to find the code to make my validation work.

Is there a JS command to invoke the form based validation and check for null on all the fields I have set to 'User Required'?

Thanks

Ellis