can anyone please help me..how to assign langitude and longitude on customer record automatically. is there some NetSuite feature available? Or can i do via script if yes then how?. Thanks in advance

You should be able to make a request to the google api with the information from the address sublist on the customer level. Something close to the below should get you in correct direction

var requestString = '<https://maps.googleapis.com/maps/api/geocode/json?address='+addrString+cityString+stateString>;
            nlapiLogExecution('debug','Details','requestString = '+requestString);
            var response = nlapiRequestURL(requestString);

@Sandii thank you so much.