How to select a specific field via vbscript

I'm looking to be able to select a specific field in a PDF and set it's value, as opposed to looping through all of the fields and looking for a specific field name (in VBScript (I'm just a sys admin trying to streamline a task involving filling out many PDF documents, I'm not a developer)

In other words, I'd like to replace this (which works):

On Error Goto 0
FileNm = "C:\Temp\DOC.pdf" 
Set AVDoc = CreateObject("AcroExch.AVDoc") 
If AVDoc.Open(FileNm,"") Then
    Set pdDoc = avDoc.GetPDDoc() 
    Set PDFForm = CreateObject("AFormAut.App")
    Set x = PDFForm.Fields
    For Each myField In x
        If myField.Name = "Text100" Then myField.Value = "something interesting"
    Next
End If

with something like:

On Error Goto 0
FileNm = "C:\Temp\DOC.pdf"
Set AVDoc = CreateObject("AcroExch.AVDoc") 
If AVDoc.Open(FileNm,"") Then
    Set pdDoc = avDoc.GetPDDoc() 'actual PDF document
    Set PDFForm = CreateObject("AFormAut.App")
    Set x = PDFForm.Fields
    Set myField= x.getfieldname("Text100")  '<== this is the line I'm trying to figure out
    myField.Value = "something interesting"
End If

Can it be done?

And thanks!