changing FXField radius and unwanted results

I did the following :

-- create FXField with force 1, but want it to be inactive, thus set radius to 0 :  
PC.CreateFXField("field", 0, x, y, 1, 0, false, 1 )  
myfield= PC.GetFXField("field")  
  
-- later want my field to be there, and :  
myfield.radius = 50  
  
--\> the UNWANTED effect : force is getting tremendous  

How should I do then ? [import]uid: 9328 topic_id: 26726 reply_id: 326726[/import]