Change icon for item charges

[ALiEN95]

how can u change icon in witch says (for example) how much potions you have left

(i would like to change it because i have some stuff with 1200 charges and it would be more visible if that icon is changed (to full black)

xD

 

[XPQJ]

have 2 items with the same effect and different icons and just have a trigger switch them at X amount of charges