Read the developer help file in ACAD!!!!!!!!!!!!!!!!!!!!!!! Help, develper help. From the top menu.
This is an excellent source of information. This is why ACAD is so much more than ACAD LT. Take a look, it will help you quite a bit.
Sub Example_Diameter()
' This example creates a Circle object in model space and
' returns the diameter of the new Circle
Dim circleObj As AcadCircle
Dim centerPoint(0 To 2) As Double
Dim radius As Double
' Define the new Circle object
centerPoint(0) = 0: centerPoint(1) = 0: centerPoint(2) = 0
radius = 5#
' Create the Circle object in model space
Set circleObj = ThisDrawing.ModelSpace.AddCircle(centerPoint, radius)
ThisDrawing.Application.ZoomAll
MsgBox "The diameter of the new Circle is: " & circleObj.Diameter
End Sub
Sub Example_Center()
Dim circObj As AcadCircle
Dim currCenterPt(0 To 2) As Double
Dim newCenterPt(0 To 2) As Double
Dim radius As Double
' Define the initial center point and radius for the circle
currCenterPt(0) = 20: currCenterPt(1) = 30: currCenterPt(2) = 0
radius = 3
' Create the circle in modelspace
Set circObj = ThisDrawing.ModelSpace.AddCircle(currCenterPt, radius)
ZoomAll
MsgBox "The center point of the circle is " & currCenterPt(0) & ", " & currCenterPt(1) & ", " & currCenterPt(2), vbInformation, "Center Example"
' Change the center point of the circle
newCenterPt(0) = 25: newCenterPt(1) = 25: newCenterPt(2) = 0
circObj.center = newCenterPt
circObj.Update
' Query the results of the new center position
' Notice the output from the center property is a variant
Dim centerPoint As Variant
centerPoint = circObj.center
MsgBox "The center point of the circle is " & centerPoint(0) & ", " & centerPoint(1) & ", " & centerPoint(2), vbInformation, "Center Example"
End Sub