Unfortunately, it's a site wide control and not something forum specific that can be assigned differently in different places.

Looking at the one active thread you have there right now Charlie, I see the two updates you posted.

This is a perfect example of what I mentioned above. If you would like the original post edited to reflect those updates, I (and I'll assume the rest of the staff) would be very happy to accommodate those requests.  As items get sold off, or if you want to change prices etc. simply send me a PM and I can easily get that sorted for you.

*Having said that, as more people list things for sale over time, your thread will become buried on the page and editing the original post will not bump it back to the top.