I have a site where users earn commissions through referral of ad placements
Once their commission gets up to $25 they can choose to redeem their commission through issuance of gift vouchers.
I'm using Gravity forms for them to fill out a form to request to redeem their commission.
In the form they can select 2 stores that they want a gift voucher for and then enter the value they want to spend in each store.
The problem is that I need to validate the form so the total amount of these 2 fields is not greater than their total commission balance which is passed to the form through a $_GET value.
eg. If my commission balance is $40.00, then the combined total of the 2 fields can't be more than 40
I am embedding my form into a page template using do_shortcode
echo do_shortcode(" [gravityforms id=7 title='false' description='false' field_values='commission_value=".$_GET['balance'].");
Can you give any advice on how I can hook into the form validation to validate these fields?