geocoder prevent overwrite of existing values

Hi all,

As mentioned in an earlier post I have an issue with google maps and businesses with the same postcode. I am assuming that I can overcome this by amending the lat and long for each business where there is a conflict, a daunting and time consuming task to say the least but likely to be the only solution.  The problem is that if I change the latitude etc once the record is changed and saved geocoder changes it back to its own calculated results.  Is there a way to prevent geocoder amending the values if the values already exist and only performing the calculation when there is no value in the fields.

Thanks in advance.