Wordpress Woocommerce add coupon code programmatically after Submit Apply Coupon?

Wordpress Woocommerce add coupon code programmatically after Submit Apply
Coupon?

I am making Wordpress WC plugin, I went through how to add coupon code
through programmatically.
But i want to add coupon code just after user click on coupon apply button
and then its get applied that code.
for that i am using
add_action('woocommerce_get_shop_coupon_data','myfunction')
but it will add coupon code more than 1 times.
Please help me and let me know which action should i call in my plugin.