OBJECT.CreateEllipticalRegion(Rectangle,[Angle] , [Resolution] , [Style] )
OBJECT:FeatureFactory对象；
Rectangle（矩形）：Rectangle对象，确定了椭圆的大小；
Angle（角度）：变量，决定椭圆绕中心点旋转的角度；
Resolution（精度） ：变量， 椭圆的精度，由多少点构成；
Style（样式）: 变量，定义了所画椭圆的样式，如颜色，线型等。
实际编码：
Private Sub Map1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
If Button = vbLeftButton And (Map1.CurrentTool = miAddEllipseTool) Then
　Map1.NumericCoordSys.Set miLongLat, 0
　'将屏幕坐标转变为经纬度坐标
　Map1.ConvertCoord X, Y, RectX1, RectY1, miScreenToMap
　End if
End Sub
Private Sub Map1_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
　If Button = vbLeftButton And (Map1.CurrentTool = miAddEllipseTool) Then
　　'将地图的坐标系统设为经/纬度坐标
　　Map1.NumericCoordSys.Set miLongLat, 0
　　'将屏幕坐标转变为经纬度坐标
　　Map1.ConvertCoord X, Y, RectX2, RectY2, miScreenToMap
　　'鼠标弹起时，画椭圆
　　Call AddEllipse(form1,RectX1,RectY1,RectX2,RectY2)
　Endif
End sub

'画椭圆过程
Public Sub AddEllipse(frm As Form, x1 As Double, _
y1 As Double,x2 As Double,y2 As Double, EditLayer As Variant)
　Dim RECT As New MapXLib.Rectangle '画椭圆的矩形框
　Dim CreatedEllipse As Feature '所画的椭圆
　Dim I as integer,EditLayer as integer
　'设置画椭圆的矩形框
　RECT.Set x1, y1, x2, y2
　With frm.Map1
　　'创建椭圆
　　Set CreatedEllipse = .FeatureFactory. _
　　CreateEllipticalRegion(RECT, , 500, .DefaultStyle)
　　'确定哪一层是可编辑层，椭圆只能画在可编辑层上
　　For I=1 to .map1.layers.count
　　　If .map1.layers(I).editable=true then
　　　　Editlayer=I
　　　　Exit for
　　　Endif
　　Next I
　　'将椭圆添加到所画的图层上
　　.Layers.Item(EditLayer).AddFeature CreatedEllipse
　End With
End Sub