Assigning a dynamic tag on an adjustment

[Hydrothermal]

I'm trying to add an adjustment that lets you select a slot and add more copies of it. My adjustment uses the custom menu expression ExtraSlot.Eqp? to get a list of all extra slot tags. I copied some code from the Weapon Focus feat and tried this:

doneif (tagis[Helper.FtDisable] <> 0)
doneif (field[pChosen].ischosen = 0)

var x as number
var slot as string

call fTargetId

for x = 1 to field[pAdjust].value
    perform field[pChosen].chosen.setfocus
    perform hero.assignstr["ExtraSlot." & slot]
next

Unfortunately it appears that fTargetId always looks for the usrChosen1 field, and the user menu field for adjustments is named pChosen instead. I could of course just write an if/elseif block to assign the right tag for every slot, but I'm sure there's a more elegant solution. Is there another way to assign a tag from the user menu?

[Mathias]

doneif (field[pChosen].ischosen = 0)

perform field[pChosen].chosen.pulltags[ExtraSlot.?]

var i as number
for i = 1 to field[pAdjust].value
  perform hero.pushtags[ExtraSlot.?]
  next