Weird problem with replaceitemvalue

I have an agent that is creating a document. There are fields int he doc called nada, nada_1, nada_2 …up to nada_47. My agent is using a variable counter to populate these fields when an associated line is going to be empty…the command I’m using is :

call doc2.replaceitemvalue(“nada_”&y,“nodata”)…if y=2, the field nada_2 should be populated with “nodata”…what is happening though, is the agent is creating a field in the document that is actually called ‘doc2.nada_2’ and setting that to equal “nodata”

I have other fields aa_ that are being created properly with the same command. Any thoughts?