Freeze Layer

I'm working on a project where the architect wants us to freeze alot of layers. When he send us an updated back ground we have to freeze these layers once more. Is there a way to freeze these layer automaticly before inserting the new back ground? And if there is how do I do it? I'm using Auto Cadd 2008.

Thank you.

here is how we go about it:

all our background files are called e.g. X-base or background or whatever. Than whenever we get get a new background file i rename the old one (add "-old" to the name or a date) than "save as" the new background file as the X-base or background or whatever. That way all layers, as the filename never changed, should be frozen according to the previous settings.

Hope that helps.

I will try that thank you.