How Do I Capture The Date An Online Customer Form is Submitted?

Hi

I wish to attempt to create some marketing automation in Netsuite (within its limitations for this).

I want to schedule marketing campaigns daily - based on Groups, which are dynamic - i.e. based on saved searches. The saved search needs to look for the relevant Campaign Code, plus the date that the online customer form was submitted (the form submission could either create a new Prospect, or add data to an existing one).

Can someone please tell me how I can store the date that the form was submitted in a custom field? I know I could use an Online Case Form, which has such dates - however that creates to other challanges when creating new records (which get flagged as unsubscribed). I hav created a custom date fied - I have no idea how to default this to today's date on the form. I am sure scripting could do it - I have no idea about scripting