How do I improve the crit range for a certain material?

[Azhrei]

I have a new material that works a lot like obsidian, but it adds 1 point to the critical range of the weapon. So my scimitar, made of this material, would crit on 17-20, not 18-20. But how do I code this?

I noticed that the original obsidian material has an eval script. It's apparently calling functions defined elsewhere, but I'm not sure why the first one is there at all.

perform container.parent.setfocus

~ Our parent becomes Fragile
perform focus.assign[wSpecial.Fragile]

I've looked at the Improved Critical feat, but this is all greek to me! It does appear that I will need to combine the "perform container.parent.setfocus" from above with some part of the code below... Maybe this line is all I need, but somehow replacing 'each pick' with the parent? "perform eachpick.assign[Broadcast.ImpCrit]"

~ If we're disabled, do nothing
doneif (tagis[Helper.FtDisable] <> 0)
var name as string

~ If we haven't chosen anything, get out now
doneif (field[usrChosen1].ischosen + tagis[Target.?] = 0)

if (tagcount[Hero.MartVersa] + hero.tagcount[Hero.MartMaster] <> 0) then
  perform field[usrChosen1].chosen.pulltags[wFtrGroup.?]

  ~ this call takes care of mythic martial versatility and mythic martial mastery
  call MytMartial

  foreach pick in hero from BaseWep
    if (eachpick.tagmatch[wFtrGroup,wFtrGroup,initial] <> 0) then
      perform eachpick.assign[Broadcast.ImpCrit]
      perform eachpick.pulltags[ImpCrit.?]
      endif
    nexteach

  name = this.tagnames[wFtrGroup.?, ", "]
  perform hero.pushtags[ImpCrit.?]
else
  ~ Assign the appropriate tag to all weapons that meet the criteria
  var id as string
  call fTargetId
  foreach pick in hero where "IsWeapon." & id
    perform eachpick.assign[Broadcast.ImpCrit]
  nexteach

  ~ Forward the improved critical tag for the weapon to the hero
  perform hero.assignstr["ImpCrit." & id]
endif

~ Set our 'short name'
field[shortname].text = "Imp Crit: " & name

if (field[sbName].isempty <> 0) then
  field[sbName].text = "Improved Critical (" & lowercase(name) & ")"
endif