subtotal cart wrong

Hi,

I've got a problem with the subtotals in my shopping cart. I'm using the cost per letter attribute and modified it so it can be used for the length of the item. So when a customer fills in 1000 the price is calculated as being 1000 x 'price per letter', instead of 4 x 'price per letter'. When I use this, the subtotal in my shopping cart is wrong, see:

http://ipdata.biz/shop/index.php?main_page=product_info&cPath=10_22&products_id=263

When i disable this attribute and just use a normal price, the subtotal is ok. See:
http://ipdata.biz/shop/index.php?main_page=product_info&cPath=10_22&products_id=256

Can anybody explain this to me? Thanks!

Ok, now I've got it partially right. When I order just one item the total is correct (don't now why it's correct now, I just entered all the values again). But when I add a second item, the subtotal is way off. For example, when I order one item of 3 euro, the subtotal is 3,60 (incl VAT - correct). But when I order a second item with a price of 0,30 euro the subtotal is 1,30 euro (wrong). And when I just order the second item alone, the subtotal is 0,36 euro (correct). What's happening here???

Thanks,

JAN

:frusty: Never mind... I followed everything in this post:
http://www.zen-cart.com/forum/showthread.php?t=33423

The part line 561 messed things up...