I would make a boolean variable called start as well so that when 100 gold is reached you could set start to false and add that to the condition. Else during the game everytime it gets below 100 this event would fire.
Every 0.05 seconds - if gold is < 100 - start = true - add 1 to gold
if gold = 100 - set start to false
System every tick - Set text to "gold :"&player.gold