MapDisplay md = ESRI.ArcGISExplorer.Application.Application.ActiveMapDisplay;
bool var = false;
FeatureLayer lr = null;
for (int i = 0; i < md.Map.GetMapItems<Layer>().Count; i++)
{
lr = md.Map.GetMapItems<FeatureLayer>();
if (lr.Name.Trim().StartsWith("MY_LAYER")) break;
}
lr.Connect();
PopupFeatureLayerProperties ppp = lr.PopupProperties;
//I leave last two fields here, but you can play as u want with "ppp.PopupFields" add-remove it.d.
while(ppp.PopupFields.Count > 2) ppp.PopupFields.RemoveAt(0);
Is it a top-secrete government level property or you should fire the guy who does documentation...? cheers!