Lastactivity query

Can anyone please tell me what is wrong with this line of code?

PHP Code:

AND lastactivity>'.$lastposttime[dateline]-(86400*30).' 

I am trying to make it so the query will not return the same name over for at least 30 days. If the username has been picked, I don't want his name drawn again for at least another 30 days. Once a month, I guess is what I mean. I think I'm close but I haven't quite got it yet. Anyone have any ideas what I might be missing or doing wrong?

Do I need to use lastvisit instead?

[Xenon]

user brackets around the term

PHP Code:

($lastposttime[dateline]-(86400*30)) 

[Boofo]

Like this?

PHP Code:

AND lastactivity>($lastposttime[dateline]-(86400*30)) 

And will that only pick the same username after 30 days and not before?

[Xenon]

nope, just add the brackets to your original query, don't touch the '.

[Boofo]

So you mean like this then.

PHP Code:

AND lastactivity>'.($lastposttime[dateline]-(86400*30)).' 

[Xenon]

yes

[Boofo]

Thank you, sir.