Can someone please help

[Hex_legend]

Ok,
so I have a field that says "Do you have a shop at XXX site?" Yes / No
when they say yes, they put their username in for that site and it shows up with the link to their shop.

The next field says "Would you like to place a community banner to help promote XXX?" Yes / No
This also enters their shop name and adds it to a pre-defined URL.

However, I am having members say No to having a shop but saying yes to the displaying of the banner, which leads to a 404 not found.

What condition do I use to check both fields say yes to check that a shop actually does exist or nothing is displayed?

Here is the code I am using at the moment for one field

PHP Code:

<if condition="$post['field8']==Yes"><a target="_blank" href="http://www.XXXX/shop/$post[field6]"><img src="http://XXXXX/forum/foundat.png" border="0"></a></if> 


Any help and code snippits are greatly appreciated