How to set up a randomized battle system?

Danicron

Ok so im trying to figure out a Battle System, this system is unseen other than to an Battle log box, so i dont have any animation or anything to have to mess about at. However my goal is to use a sort-of Dice roll system to decide how each Dungeon/Level will turn out. So i thought perhaps the best way to do that would be to type it sort-of like this (this is only a guess i haven't tried this yet)

func quest_events():
	Randomize()
	Randi (range(1, 101))
	if (random_number <= 30)
		Battle()
		quest_events()  < -------  this is me trying to start the roll again after the battle (but i dont think it looks right)
	if (random_number > 30 && <+ =50)
		player.get_chest()
		quest_events() 
	if (random_number > 50 && <=75)
		Boss_Battle()
		quest_events()
func Battle():
	pass	

func Boss_Battle()
	pass

i also wanted to figure out a way that i can make sure not to get a boss battle straight away for the first one or two rolls so i was thinking a match statement but im not sure if thats how it works Any help at all would be appreciated :)

Edit : And i just realised i asked the totally wrong question for the title that i set....... -_-

Additional :

flame-cube

I'm not sure about the rest, but there is a way to make sure there is no boss fight on the first attempt. So make a variable called rolls, and set it to 0, but every time you run the function, increase it by one. Then do

if (random_number > 50 && <=75 && rolls > 1)
    Boss_Battle()
    quest_events()