coding query

[Greylin]

Sorry for a very basic question, but I want the below eval script for sneak attack bonus to cap out at +3d6 at 15th level rather than incrementing to +4d6 at 20th. How might I put in a 'max 3' limit please?

--snip--
~ Add our level / 5 to our sneak attack damage.
var sneak as number
sneak = field[xTotalLev].value / 5
sneak = round(sneak, 0, -1)
hero.child[xSneakAtt].field[Value].value = hero.child[xSneakAtt].field[Value].value + sneak
field[livename].text = "Sneak Attack +" & sneak & "d6"
field[CustDesc].text = "+" & sneak & "d6 to your Sneak Attack damage."