Q:

LookUpRows on rowset created with function BuildRowSetFromString

Is it possible to apply a function like LookUpRows or Lookup to an array created with BuildRowSetFromString? 
I have this: 
SET @rowSet = BuildRowSetFromString(@ItemsString2, '|')

I'd like to know if there's a function on which I can do: 
SET @var = LookupRows(@rowSet, ITEM_ID, ... ) 

I am trying already using a FOR loop. I want to know if there's a function that can do this. 

A:

No. I wish.  
Best bet would be to use arrays in Server-Side JavaScript or possibly GTL.
If you want to over-engineer it, you can use XML and XPATH to do some array functions in AMPScript.  I've written up a use-case with examples here on my personal blog.
Also, there is a lot more SFMC dicussion going on over in http://salesforce.stackexchange.com.

