Hi all... this is my first time using the user group so I'm not overly
sure if I'm posting this correctly. Anyway I'm in urgent need of help!

Here's our problem...

Say I have a certain Category of products named 'dogs'.

And this may contain such products as 'bulldog', 'pitball', 'border
collie' and 'australian silky', etc etc.

How can I set the condition that if any 6 products are purchased from
'dogs', 2 of these will be free?
In other words, a 'buy 4 get 2 free' deal - but only for a certain
category.

We need these to be made available to all customers, new or returning. -
I've looked into coupons from vikingcoders which had similar
functionality, but we don't want the customer to have to enter coupon
codes.

Thanks in advance!