lock until point reached then when clicked on deduct points

Ohk the system I am using is quite complicated but here it goes. To put it simple I have a button that when you click on it spawns a gameobject. I am using OnGUI to draw my gui buttons. I have a score script that just shows how many points you havem(attached at the bottom) I will at Now to the question how would I be able to lock a gui button until I have a certain amount of points then unlock the button? And then when the button is clicked it will deduct a certain amount of points.

Score script:

static var SCORE : int = 0; function OnGUI () { GUI.Label (Rect (10, 10, 100, 20), SCORE.ToString()); }

If you need the button script the please just comment and ask because it is not the convetional button script.