change the geometry of the vertex point added by the sketch view model

[siefaqel]

Hi, i am trying to make any change on the vertex point showed by the sketch view model after adding a vertex to the polyline that the sketch view model is creating -check the screenshot below-, is there any way that i can hide or change it's geometry or the geometry of the black and white guide line that Sketch-VM shows on the map when creating a polyline without using snapping property?

Note: the blue line is the actual graphic that the Sketch-VM is creating -check the other screenshot- but i change it's geometry.