I'm having problems updating values in TList.

SuperStrict

Type TTile
	Field xpos_i:Int
	Field ypos_i:Int
	Field zpos_i:Int
	Field tileColor:String
'	Field pic:TImage
End Type

Type TEngine Extends TTile
	Global Tilelist:TList = New TList

	Method GoThruListBackwards() 
	   Local LastTEngineObject:TLink
	   Local CurrentTEngineObject:TLink
	   Local lstObject:TEngine
	
	   LastTEngineObject = Tilelist.LastLink() 
	   lstObject = TEngine(LastTEngineObject._value) 
			
	   While True 
			lstObject.ypos_i:+55   '***This Doesn't Take***

			CurrentTEngineObject = LastTEngineObject.PrevLink() 
			If CurrentTEngineObject = Null
				Exit
		    EndIf
			lstObject = TEngine(CurrentTEngineObject._value) 
	
			LastTEngineObject = CurrentTEngineObject
		Wend

           '**When I iterate thru the list my ypos hasn't been
           '**updated
       For Local k:TTile = EachIn TileList
			DebugLog k.ypos_i
       Next

	End Method
	
	Method AddTile(t:TTile)
		Tilelist.AddLast(t)	
	End Method
	
End Type


Local eng:TEngine = New TEngine

eng.AddTile(New TEngine)
eng.AddTile(New TEngine)

eng.GoThruListBackwards()

eng.GoThruListBackwards()