plot dots on a google map with the size proportional to the map scale

I plot some dots on google map using 'plot_google_map.m' function , the function use 'makescale.m' function to make scale for the map and scale variable has call back functionality. Now I want to change my dot size corresponding to the scale. for example if the scale is 200000(m) my dot size is smaller and when the scale is less my dot size are larger. I think I need to use the local variable 'scale' and add call back functionality to my dot size variable and then plot dots by scatter plot. Not sure how to do these. Any help will be appreciated. Thanks