Force currency on checkout only for specific currencies

Hi,

I am using the pro version of the plugin with multiple currencies. Couple of the currencies that I use are not supported by the payment processor. What is the code to force supported currency on checkout only when user has an unsupported currency selected?

I found this for forcing a currency on checkout but it forces for all currencies:

add_filter(‘wp_head’,function(){
if(is_checkout()){
global $WOOCS;
$WOOCS->set_currency(‘USD’);
}
});

I guess can be solved easily with if else statements.

Thanks,
Marko