The best information you will find about nodes is in the help file. There are several examples for what you want....

Adding a node to a SubPath

Code:

Dim sp As SubPath
For Each sp In ActiveShape.Curve.Subpaths
sp.AddNodeAt 0.5, cdrRelativeSegmentOffset
Next sp

Adding a node to a Segment

Code:

Dim s As Shape
Set s = ActiveLayer.CreateCurveSegment(2, 8.3, 5.3, 8.5, 1.5, -62,
2.4, 84)
s.Curve.Segments(1).AddNodeAt 0.5, cdrRelativeSegmentOffset

Delete a Node

Code:

Dim s As Shape
Dim n As Node
Dim i As Long, Num As Long
Set s = ActiveShape
If s.Type <> cdrCurveShape Then Exit Sub
Num = s.Curve.Nodes.Count
i = 1
While i <= Num
Set n = s.Curve.Nodes(i)
If n.Type = cdrCuspNode Then
If n.SubPath.Nodes.Count = 2 Then
' Deleting a node from a segment containing only 2 nodes
' will remove the whole segment. If we are deleting the last
' node of the subpath, then we must move one more step back.
If n.SubPath.EndNode Is n Then i = i - 1
n.Delete
Num = Num - 2
i = i - 1
Else
' Just delete the node and adjust the number of nodes left.
n.Delete
Num = Num - 1
i = i - 1
End If
End If
i = i + 1
Wend

There are many many more examples that should help you out in the help file!

-Shelby