If you did not understand that(I am horrible at explaining things) try this makeshift code I just coded that I know will not work because it would say d.goldcoins is undefined.
set category = "GM"
if(usr.key != "SadoSoldier")
alert("Sending players coins, without my permission, WILL result in a ban no matter who you are!")
var/d = input("Please input their key:") as text
var/c = input("How many Gold Coins?") as num
d.goldcoins += c
usr<<"<b>There is noone by that key!"
That is just an example, so how would I go about this?