How to check if product url field is empty or not!

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Hey guys!
I made changes to the product page in which when the virtuemart is used as catalog, the "url" is showing insted of "add to cart" button. Now i'm trying to make some more changes to the product page to check if the "url" field is empty, act differently. something like this:

If a url is set for the product--> show statement 1 (which i already managed to get this)
but if the product filed is left empty ---> show statement 2

any idea guys?!