I'm guessing this is in the "Item Selection" part where it says "Custom Expression".

Is there an example of this in use? Or maybe just some help modifying one of the statements?

This is the primary statement I'm working with in the Eval Script:

perform hero.child[wClaw].assign[wMain.2d6_104]

so if I make a "custom expression" called 'primary' how would I modify that statement to target the field primary?

What's your overall goal here? I can't see what you're trying to accomplish with all this.

(in game terms, not Hero Lab terms)

Alright. This is a paragon class, basically instead of taking levels in Ranger, Monk, Wizard, etc you take levels in your race (but its not a monster class).
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This class grants the race claw attacks that increase in damage similar to a monks unarmed strike. It also grants a bite and gore attack (levels 4 and 9 respectively) that also increases (at the same level, which is different from the claws) in damage. All these attacks are primary natural attacks.

It has abilities called enticements which let you select new abilities for customizing your character. One ability grants an additional set of arms and a claw attack that is considered a secondary natural attack. There is an enticement that can add a tail slam attack also as a secondary attack. There are also enticements that change the new claws into primary attacks (you have to take it once for each set of claws you want to convert) also enticements to raise the bite, gore and tail attacks to do the same damage as the claws. There is also an ability that lets you select a set of claws and that set is considered adamantine, it can be taken a number of times equal to the pairs of claws you have.

The enticements also contain abilities such as granting Acid Resistance that turns into Immunity if the level is >= 10. An acid breath weapon that does 1d6 damage/2 levels. An ability that adds 1d6 acid damage to your tail slam every time you take it (max 5d6). An ability that adds +2 damage to claw attacks. An ability that doubles the amount of acid damage being dealt. One that adds DR 5/magic each time you take it (max 15/magic). An ability that grants a spell like ability of a spell from the Earth subschool.

I think that's everything for the most part, I attached my user file (as a zip) if anyone wants to take a look at it.

Thanks
Andrew

Can you take additional arms more than once?

Yep, it has a minimum level of 6, but there is no limit (besides the number of enticements you have available).

Okay - if it were selectable only once, that would mean that the user didn't need to select which set of additional arms was now primary - there'd only be one set to find.

Actually, thinking about it further, there is a way to accomplish this without the user needing to select a specific set of claws to improve.

Alright. When you set up your additional arms ability, add a custom tag to it. Let's say SWAddArm.

Now, when you bootstrap the claw attack from that ability, press the Tags button, add a new tag, and give it that Custom tag you've defined:

group id: Custom, tag id: SWAddArm

You'll also force that claw to always be secondary:
group id: Helper, tag id: NatOverSec

On the "make our new claws primary attacks" you'll search through all the claw attacks on the hero that have been given that Custom tag:

phase: Pre-Levels, priority: 5000
According to the Bestiary, pg. 302, claws default to primary, so that's the behavior Hero Lab follows - once you delete Helper.NatOverSec, the claws will revert to being primary natural attacks.

It should also work if you add multiple copies of "make our new claws primary attacks" - each copy will find and make primary only one set of claws.

For the immunities and breath weapon, take a look at the Sorcerer's draconic bloodline - that's also got a breath weapon, and it's got energy resistances up to a certain level that are replaced by immunities beyond that.

I'm getting an error of:
Hero Lab was forced to stop compilation after the following errors were detected:

Syntax error in 'eval' script for Thing 'cStoPowArm' (Eval Script '#1') on line 8
-> Extra characters at end of line

and I'm not finding any extra characters.

In your Eval Script, check how everything's arranged - is the "~and make sure" line the 8th line there? (empty lines count towards the line numbering).

Could you try copying your script and pasting it here - that'll make sure everything stayed the same in the copying.

Hero Lab was forced to stop compilation after the following errors were detected:

Syntax error in 'eval' script for Thing 'cStoPowArm' (Eval Script '#1') on line 12
-> Extra characters at end of line