Using Programming Languages other than VBA

Sub Example_SingleDocumentMode()
	' This example reads and modifies the preference value that controls
	' whether AutoCAD runs in single- or multiple-document mode.
	' When finished, this example resets the preference value back to
	' its original value.

	Dim ACADPref As AcadPreferencesSystem
	Dim originalValue As Variant, newValue As Variant

	' Get the system preferences object
	Set ACADPref = ThisDrawing.Application.preferences.System

	' Read and display the original value
	originalValue = ACADPref.SingleDocumentMode
	MsgBox "The SingleDocumentMode preference is set to: " & originalValue

	' Modify the SingleDocumentMode preference by toggling the value
	ACADPref.SingleDocumentMode = Not (ACADPref.SingleDocumentMode)
	newValue = ACADPref.SingleDocumentMode
	MsgBox "The SingleDocumentMode preference has been set to: " & newValue

	' Reset the preference back to its original value
	'
	' * Note: Comment out this last section to leave the change to
	'		 this preference in effect
	ACADPref.SingleDocumentMode = originalValue
	MsgBox "The SingleDocumentMode preference was reset back to: " & originalValue
End Sub