how you could override the Cart total, no matter how many products are in the Cart?

function bbloomer_force_cart_to_100() {
    $total_disc = WC()->cart->cart_contents_total - 100;
    WC()->cart->add_fee( 'force', -$total_disc );
}
add_action( 'woocommerce_cart_calculate_fees','bbloomer_force_cart_to_100' );