Make this function active when IDR currency is selected

Please help with this function, i want to this function below is active when the IDR currency is selected and when USD selected this functiion is disable

code:
function woo_add_cart_fee() { global $woocommerce; $woocommerce->cart->add_fee( __('Kode Unik', 'woocommerce'), rand(101,199) ); } add_action( 'woocommerce_before_calculate_totals', 'woo_add_cart_fee' );