Thanks for the fast and solid answer!

We don't use the import wizard for this file. Customer data should be imported like xml data files when installing or updating the module. But sometimes we don't want to import this file because the data in the database are more accurate then the incoming csv file.

So currently the only way  is too comment the line out in __openerp__.py? 

Actually this is good idea but the problem is there is no logical place at where we can add "noupdate" option for the end user who is going to upload the file.

However, we can add a check-box below csv file option at the time of import the file.

So those records which are in the csv file will be locked and those can't be updated while import the file again. 

However there are quite few more changes we need to do if we decide to customize like this way. But this is the only way to solve your purpose. If you are good programmer then you can try yourself but currently no any person has did this kind of solution so far neither as independent solution or community module.