The issue here is that he did not realized that one need to use gmap.AddMarker to get an Initialized Markerobject.
You can´t create one by code only (without using gmap).
My code
Code:
Dim MMark as Marker = gmap.AddMarker(lat,lon)
is based on the GoogeMaps-Example code
Code:
Sub gmap_Ready
btnResetMap.Enabled = True
btnJumpToEiffel.Enabled = True
For i = 1 To 10
Dim m As Marker = gmap.AddMarker(10 * i, 10 * i, "Marker #" & i)
AttachInfoWindow(m, "Some text " & i)
Next
End Sub