I could make it work!
Add this line to update the marker instead of deleting it (still impossible) and insert it again...
after my last line add
p_web.ntMap('GeneralMap','updateMarker','NewWp', p_web.GetLatLng(p_web.GetSessionValue('gm:Latitude')) , p_web.GetLatLng(p_web.GetSessionValue('gm:Longitude')) , p_web.WrapOptions(loc:options) , p_web.jsok('My Place', Net:HtmlOk*0+Net:UnsafeHtmlOk*0) , '1')
and it will do what you need.