API Google DotNet

Hello,

I am trying to create a Report Only processing, that calculates the distance between two Local Post Codes ( My Company WhareHouse and Client).
I'm using a variable dotnet getdistance from google to calculate the distance. But i have some problems.
I have more than 30k lines to calculate, and not all gives back distance different from 0.

My table structure is like this:

Customer No|PostCodeOrigin|PostCodeDestination|Distance
where
Customer No|PostCodeOrigin|PostCodeDestination is a key.


the code does something like this

MyTable.RESET;
IF MyTable.FINDSET THEN REPEAT
...
Code to get the Post Codes and other data
.....
Distance:=GetDistance(PostCodeOrigin, CountryOrigin,PostCodeDestination,CountryDestination);
IF Distance= 0 THEN
Distance:=1;// so i can know what calculation failed
Mytable.Modify;
COMMIT;
SLEEP(1000);

Until Mytable.Next=0;

How can i complement the variable distance so that if it gets 0 there can be other way to get distance by other fields of Customer and Location tables.
Then how can i pass the limit of requests . I don't know what is the limit but i guess is very little.
Or is other way of getting distance between to points in NAV?

Really need help on this one :-/