The syntax for kmlwrite is:
kmlwriteline(filename,latitude,longitude,altitude);
The fourth variable passed is considered as altitude data. In your case you can create an array with multiple lat and lon points and send that array to the function.
Try this:
lat_points = [lat1;lat2;lat3;lat4];
lon_points = [lon1;lon2;lon3;lon4];
kmlwriteline(filename,lat_points,lon_points);
Hope this helps.
