Adding custom Price in cart with any particular product

I am creating a plugin which just show some custome price of the behalf of my calculation. I only want to hide woocommerce add to cart button and price. instead of this i just put the HTML of add to cart form, and want to add my custom price in cart.

like: if my calculation show 100 then when i click on add to cart button then it just add only 100 and when any other price then add that price only.

MY HTML form code:

<form class="variations_form cart" method="post" enctype="multipart/form-data" style="display: block;">
    <div class="quantity">Cantidad: <input type="text" step="1" min="1"readonly name="quantity" value="<?php echo $total_ply2;?>" title="Cantidad" class="input-text qty text" size="4"><span> <?php echo 'Precio :' .  $total_price;?> &euro; </span></div>
    <input id="Grosor de tablero" type="hidden" name="attribute_pa_grosor-tablero" value="<?php echo $_POST['var-slug']; ?>" />     

        <input type="hidden" name="add-to-cart" value="<?php global $product; echo $product->id; ?>">
    <input type="hidden" name="product_id" value="<?php global $product; echo $product->id; ?>">
    <input type="hidden" name="border_price" value="<?php echo $total_border_price; ?>">
    <input type="hidden" name="row" value="<?php echo $prod_str; ?> " id="prod_str">
    <input type="hidden" name="variation_id" class="variation_id" value="<?php echo $_POST['curr_variation_id']; //echo $variation_id; ?>">
    <input type="submit" name="my_price" class="single_add_to_cart_button button alt" value ="Añadir al carrito" >
    <?php include STYLESHEETPATH . "/custom-files/envio-link.php"; ?>
</form>  

via Chebli Mohamed