Blender Scale

UI position

Can UI window remember its position after restart of the max

.

Yes, every time when you click the spinner the code inside "on lbutton down do" will be executed, but why this should be a problem?
The script is yours and you will make it as you want. Here is how I see the things.
1) if you use what I posted the benefits are:
- you will get rid of the Get Vert Sel button and will simplify the workflow
- the script will work only with the currently selected object

The script creates an Undo record each time when the user click the spinner, so with or without the Get Vert Sel button, the user will have to press the UNDO as many times as he needs.

.

OK, try this then:

on sp_scaleX buttonDown do
	(
		print "sp_scaleX buttonDown"
		Check_Axis() 
		Check_Class()
		do_Hold #start
 
	)
	on sp_scaleX changed value do 
	(
		print "sp_scaleX changed value"
		BScale #X rad_center.state
	)
	on sp_scaleX entered inSpin inCancel do 
	(
		if not inCancel then do_Hold #accept Str:"Scale X" else
		(
			print "sp_scaleX entered inSpin inCancel"
			Check_Axis() 
			Check_Class()
			do_Hold #cancel
		)
	)

and check what will be printed in the maxscirpt listener.

The
on sp_scaleX buttonDown do
is executed only once, when the user press any of the spinner's buttons. So, when this happen the script will do the same as when the Get Sel Vert button is pressed, and will do it only once. Then, while the lmb is down and the value of the spinner is changed the script will execute only this:
BScale #X rad_center.state
If I am not right, in the maxscript listener you should see this, while the spinner's button is pressed:
"sp_scaleX buttonDown"
"sp_scaleX changed value"
"sp_scaleX buttonDown"
"sp_scaleX changed value"
"sp_scaleX buttonDown"
"sp_scaleX changed value"
...
but what you will see is this:
"sp_scaleX buttonDown"
"sp_scaleX changed value"
"sp_scaleX changed value"
"sp_scaleX changed value"
"sp_scaleX changed value"

.

Use this. No need to press the [Get Selected Vertices] button.

on sp_scaleX buttonDown do
	(
		Check_Axis() 
		Check_Class()
		do_Hold #start
 
	)
	on sp_scaleX changed value do BScale #X rad_center.state
	on sp_scaleX entered inSpin inCancel do 
	(
		if not inCancel then do_Hold #accept Str:"Scale X" else
		(
			Check_Axis() 
			Check_Class()
			do_Hold #cancel
		)
	)

By the way, why do you name your controls this way:

button 'btn_getsel'

When you can use this:

button btn_getsel