Yes it is possible. Maintain a secondary dom variable which will be set to
true once submit button is clicked. Now when you validate your values put a
condition before the validation to check whether the secondary dom value is
true or not.

Signature
Agni
www.infopathdev.com
(InfoPath Super Source)
> I would like to wait until the submit button is clicked as 80% of the fields
> on the form are mandatory. It's visually distracting with all the red
> outlines around each mandatory field.
>
> Is it possible to highlight the empty mandatory fields once the submit
> button is clicked?