Currently once 'Update' is clicked in the main form, it determines whether a new entry has been made in the subforms (simple tally of records before and after the Update) and if there is a new record it sends an email to our Accounts Department with the relevant information on the client and invoice (from the sub and main forms).  

I am trying to extend this one bit further though and schedule a reminder (say in 14 days) if the status of the invoice (which is the subform) remains 'Unpaid'.  

I have tried implementing it on the subform itself, but that only results in a schedule reminder when the invoice is inputted into the subform when it is the main form.  When I input into the subform no schedule reminder is generated.  

Is there any way around this, i.e. having hidden fields in the main form that can record the sub-form information and change when it changes and thus be able to trigger a schedule?  

Please help, this is a critical function for our application (as we need to do similar things in other subforms).