Google Maps - using Marker Position Changed

I have a Google Map that is displaying a marker based on lat and long coming from a database query.

I would like to allow the user to “fine tune” the location by dragging the PIN to the precise location.

I have looked at the community answers but I am confused as to how to achieve this. I have added a Dynamic Event using Marker Position Changed but I am not see the lat and long as options to bind them to two data input fields. in fact I don’t see the Market Position Changed event at all in the data listing.

How should I be doing this please ?