Creating custom ability that scales with level

[Bob G]

Hi everyone, I’m trying to create a custom ability in the editor that scales by level. The ability confers a +1 competence bonus to the Stealth skill, and then adds another +1 for every four class levels (i.e. +2 at 4th level, +3 at 8th level, etc.)

I tried using the following eval script:
#competencebonus[hero.child[skStealth].value, .value += 1]

But when tested, I get an error: “Syntax error in ‘eval’ script for Thing ‘cBLAssDri’ (Eval Script #1) on line 4 -> Invalid use of reserved word ‘hero’ in script

Do I just have the syntax messed up, or is there a better way of creating a scaling ability in the editor.

Thanks as always.