The check and print out are done separately. I figured you could use the condition for the promotion item and the game natively loads separate code to print the text when the item is used. 0x3000080 is the address the game uses to hold the ASCII value for gold so you can use the [G] command to load the prandom number. Yeah it's kinda weird, but I can't think of a better way to display the levels.
Suggestions are welcome if anyone has any
@Klok -- do this:
pick an item to sacrifice (ideally a stat boost item)
paste this somewhere in your ROM.
go to the item's location in the item use table and put in the new pointer
go to the item's location in the condition table and put a pointer from one of the promotion items
in feditor, choose a text slot to sacrifice and put "[G] levels lost" there
paste this into some free space and change the 50 07 to the text ID you used
go to the item's spot in the text table and put in the new pointer