Using Programming Languages other than VBA

Sub Example_StartUndoMark()
	' This example creates a series of lines, each with an undo marker
	' defined for it. After lines are created, you can switch to AutoCAD and type
	' the Undo command, and only one line at a time will be undone. If StartUndoMark
	' call is not made, an undo in AutoCAD will undo all the lines at once.

	Dim line As AcadLine
	Dim stPnt(0 To 2) As Double
	Dim endPnt(0 To 2) As Double
	stPnt(0) = 1: stPnt(1) = 2: stPnt(2) = 0
	endPnt(0) = 2: stPnt(1) = 1: stPnt(2) = 0

	' Create the lines
	Dim j As Integer
	For j = 0 To 3
		ThisDrawing.StartUndoMark
		Set line = ThisDrawing.ModelSpace.AddLine(stPnt, endPnt)
		stPnt(0) = stPnt(0) + 3
		endPnt(0) = endPnt(0) + 3
		ThisDrawing.EndUndoMark
	Next
	ZoomAll

End Sub