not yet a job opportunity...database messaging facility

hi gang,
I would appreciate some guidance on how much I should expect to be quoted for some help for the following. (Please note that this is not yet a job opportunity so I am not expecting anyone to quote on this information).
Essentially I need someone who can help me build a member messaging facility within a website. The idea is that visitors sign up, and can then use the facility to send a message (via a login process), to numerous other members all at once. The choice of who the message goes to would be via a criteria filter/choice system (chosen by the message writer) and hence the message would be written once but received by numerous relevant members.
I need someone to write the necessary, and to ensure I can incorporate it into an existing website, and to understand what has been built and how it behaves, and potentially how to modify it.
I suspect the PHP forum is the best place to start.
Any guidance or range on what sort of costs, or what sort of time someone might indicate, would be much appreciated.
Thanks a million gang
(PS the website owner would recieve the messages first of al, and veto them before forwarding them on (in a simplistic way))

Hmm. That isn' that complicated. I think how complex (and expensive) the project will become depends on how difficult it is to integrate it into the existing site.

Writing the code for the base module: 5 hours.
Integration: no clue.....

What you're wanting as c010depunkk says is not complex per se and depending on you existing sites setup would only require snap-in and a few links.

This sort of feature is standard on most half-decent forum packages. I would say probably a 10-20 hours for well tested, secure code written from scratch.. Much less for a hacked back version of some forum software already available.

Thank you both, thats been useful.

Anyone else think the costs/time would be much different than this?
Thanks very much