Editing a subrange of a wave automatically

Menu "TracePopup"
	"Replace Wave Between Cursors With Mean Value", ReplaceBetweenCursorsWithMean()
End

// ReplaceBetweenCursorsWithMean()
// Replaces all values between cursor A and cursor B with the average value.
// WARNING: THIS IS NOT UNDOABLE
// Create a graph. Put cursor A and cursor B on a trace in the graph.
// Right-click and choose "Replace Wave Between Cursors With Mean Value"
// from the trace popup menu.	
Function ReplaceBetweenCursorsWithMean()
	Wave/Z wA = CsrWaveRef(A)
	if (!WaveExists(wA))
		Abort "Put cursors A and B on the wave"
	endif
	Wave/Z wB = CsrWaveRef(B)
	if (!WaveExists(wB))
		Abort "Put cursor A and B on the wave"
	endif
	if (!WaveRefsEqual(wA, wB))
		Abort "But both cursor A and B on the same wave"
	endif
	
	// NOTE: This assumes that this function was invoked by right-clicking a trace
	// not from the command line or from some other procedure.
	GetLastUserMenuInfo				// Sets S_traceName
	String traceName = S_traceName
	Wave/Z clickedWave = TraceNameToWaveRef("", traceName)
	if (!WaveRefsEqual(wA, clickedWave))
		Abort "You must right-click the wave to which the cursors are attached"
	endif
	
	Variable startPoint = pcsr(A), startX = pnt2x(wA,startPoint)
	Variable endPoint = pcsr(B), endX = pnt2x(wA,endPoint)
	Variable numPoints = (startPoint - endPoint) + 1
	
	if (endPoint < startPoint)
		Variable temp = startPoint
		startPoint = endPoint
		endPoint = temp
	endif

	Variable avg = sum(wA, startX, endX) / numPoints
	wA[startPoint, endPoint] = avg
End