NSLookup - Google Sheets custom function to Perform a Network Service Lookup, using StatDNS API. From "Nslookup or dig in Google App Script" (http://stackoverflow.com/a/30610580/1677912).

NSLookup.gs

/**
 * Perform a Network Service Lookup, using StatDNS API.
 *
 * @param {"google.com"} dn    A well-formed domain name to resolve.
 * @return {String}            Resolved IP address
 * @customfunction
 */

function NSLookup(dn) {
  // From gist.github.com/mogsdad/ece531531e0ef5dc355d
  var url = "https://dns-api.org/A/%FQDN%".replace("%FQDN%",dn);
  var result = UrlFetchApp.fetch(url,{muteHttpExceptions:true});
  var rc = result.getResponseCode();
  var response = JSON.parse(result.getContentText());
  if (rc !== 200) {
    throw new Error( response.message );
  }
  var ip = response[0].value;
  return ip;
}

updated api to use https://dns-api.org.