Apply Coupon code on setup fee

I have setup the form setup fee through code and set the trail to 30 days in feed settings. Now i want to apply the discount code on below snippet. Is there any way to do this?

$submission_data['setup_fee'] = GFCommon::to_number( rgar( $entry, '67.2' ), $entry['currency'] ); 

I have a coupon code of 95$ OFF and setup FEE is same 95$. Is it will charge the subscription after trial period?