Disable buy button on 0 quantity items

[Jood]

Can anyone tell me how to disable the buy button on items with a quantity of zero? I've done a search on this with no useful results but I'm sure lots of people must have this in place.
I know I can just take the items out of stock but I would rather show them in stock but not allow the customer to buy, since taking things out of stock ruins the best seller list and I'd like my customers to know all the products we stock.
Thanks for any help.

[jpf]

There is a MOD called Free Call For Price

Alow a SOLDOUT or SHOWROOM only or CALL FOR PRICE or many other "buttons" and thus does not allow checkout on these items if you don't want to.

It will be included in OSC loaded version MS2-MAX 1.8 (when it is done) and is already included in the OSC loaded version SEC 2.0