OK when I was a kid I saw a film and the film was about the characters pretending to be the brady bunch but I can remember the name of the film

There's a comedy that came out in the 90's - 'The Brady Bunch Movie' - it has the family living like they did in the 60's (70's?), but they're in the present time - it's totally funny (at least I thought it was when I watched it back then.. ) is this what you're looking for?
The Brady Bunch Movie (1995) - IMDb (http://www.imdb.com/title/tt0112572/)

No I have watched that one this film I am talking about is about acotrs who apply for the roles in the brady bunch

Okay - what about this one? I haven't seen it myself, but it looks like it's a movie about the actors themselves, and their experience with the show...
Growing Up Brady (TV 2000) - IMDb (http://www.imdb.com/title/tt0228351/)