Alter items price (not to show Free)

I didn’t have any price for items on my WP theme so it end up showing “Free”.
I added a Custom code to hide price for items (end up doing all):

.price {visibility:hidden}

Is there a way to alter it into if price > 0, do nothing
and if price =/< 0 show Price Unavailable?
Or css can’t do it.

(Basically do nothing if there is a price on the item, and show “Price Unavailable” to items without entered price)

thanks