shooping cart minium

[ruisonika]

Hello,
In shopping-cart-product-line.tpl how can i increase or decrease quantities with $product.minimal_quantity.
Example:
I have a product that minimal order is 3.
So i ordered it but in cart resume i've decided to increase the quantity of that product...and i click in plus sign it increase 1 (but i wanna increase 3 - because i only can buy 3 on 3 and so on...)
How can i achive this?

 

<td class="cart_quantity text-center" data-title="{l s='Quantity'}">
		{if (isset($cannotModify) && $cannotModify == 1)}
			<span>
				{if $quantityDisplayed == 0 AND isset($customizedDatas.$productId.$productAttributeId)}
					{$product.customizationQuantityTotal}
				{else}
					{$product.cart_quantity-$quantityDisplayed}
				{/if}
			</span>
		{else}
			{if isset($customizedDatas.$productId.$productAttributeId) AND $quantityDisplayed == 0}
				<span id="cart_quantity_custom_{$product.id_product}_{$product.id_product_attribute}_{$product.id_address_delivery|intval}" >{$product.customizationQuantityTotal}</span>
			{/if}
			{if !isset($customizedDatas.$productId.$productAttributeId) OR $quantityDisplayed > 0}

				<input type="hidden" value="{if $quantityDisplayed == 0 AND isset($customizedDatas.$productId.$productAttributeId)}{$customizedDatas.$productId.$productAttributeId|@count}{else}{$product.cart_quantity-$quantityDisplayed}{/if}" name="quantity_{$product.id_product}_{$product.id_product_attribute}_{if $quantityDisplayed > 0}nocustom{else}0{/if}_{$product.id_address_delivery|intval}_hidden" />
				<input size="2" type="text" autocomplete="off" class="cart_quantity_input form-control grey" value="{if $quantityDisplayed == 0 AND isset($customizedDatas.$productId.$productAttributeId)}{$customizedDatas.$productId.$productAttributeId|@count}{else}{$product.cart_quantity-$quantityDisplayed}{/if}"  name="quantity_{$product.id_product}_{$product.id_product_attribute}_{if $quantityDisplayed > 0}nocustom{else}0{/if}_{$product.id_address_delivery|intval}" />
				<div class="cart_quantity_button clearfix">
				{if $product.minimal_quantity < ($product.cart_quantity-$quantityDisplayed) OR $product.minimal_quantity <= 1}
					<a rel="nofollow" class="cart_quantity_down btn btn-default button-minus" id="cart_quantity_down_{$product.id_product}_{$product.id_product_attribute}_{if $quantityDisplayed > 0}nocustom{else}0{/if}_{$product.id_address_delivery|intval}" href="{$link->getPageLink('cart', true, NULL, "add=1&amp;id_product={$product.id_product|intval}&amp;ipa={$product.id_product_attribute|intval}&amp;id_address_delivery={$product.id_address_delivery|intval}&amp;op=down&amp;token={$token_cart}")|escape:'html':'UTF-8'}" title="{l s='Subtract'}">
				<span><i class="icon-minus" ></i></span>
				</a>
				{else}
					<a class="cart_quantity_down btn btn-default button-minus disabled" href="#" id="cart_quantity_down_{$product.id_product}_{$product.id_product_attribute}_{if $quantityDisplayed > 0}nocustom{else}0{/if}_{$product.id_address_delivery|intval}" title="{l s='You must purchase a minimum of %d of this product.' sprintf=$product.minimal_quantity}">
					<span><i class="icon-minus" ></i></span>
				</a>
				{/if}
                	<a rel="nofollow" class="cart_quantity_up btn btn-default button-plus" id="cart_quantity_up_{$product.id_product}_{$product.id_product_attribute}_{if $quantityDisplayed > 0}nocustom{else}0{/if}_{$product.id_address_delivery|intval}" href="{$link->getPageLink('cart', true, NULL, "add=1&amp;id_product={$product.id_product|intval}&amp;ipa={$product.id_product_attribute|intval}&amp;id_address_delivery={$product.id_address_delivery|intval}&amp;token={$token_cart}")|escape:'html':'UTF-8'}" title="{l s='Add'}"><span><i class="icon-plus" style="padding:.7em;"></i></span></a>
				</div>
			{/if}
		{/if}
	</td>

Thanks for all the help.